jQuery slideshow plugin (responsive version with CSS3 optimized animation)

example.css

/* main container: */

#test {
    clear: both;
    width: 100%;
    min-width: 240px;
    max-width: 790px;
    height: 320px;
    overflow: hidden;
    font-family: Verdana, Arial;
    position: relative;
}

#test .slide {
    display: none;
    overflow: hidden;
    height: inherit;
    width: 100%;
    position: absolute;
    left: 0%;
}

#test .slide img {
    width: 640px;
    position: absolute;
    left: 50%;
    margin-left: -320px;
}

@media (max-width:320px) {
    #test { height: 150px; }
    #test .slide img {
        width: 320px;
        margin-left: -160px;
    }
}

@media (min-width:640px) {
    #test { height: 450px; }
    #test .slide img {
        width: 800px;
        margin-left: -400px;
    }
}

/* toggle button: */

#test .toggle {
    position: absolute;
    top: 8px;
    right: 8px;
    width: 30px;
    height: 30px;
    font-size: 15px;
    font-weight: bold;
    color: white;
    text-align: center;
    line-height: 28px;
    background: black;
    opacity: 0.5;
    cursor: pointer;
    border-radius: 5px;
}

/* index buttons (1, 2, 3...) */

#test .buttons {
    position: absolute;
    height: 32px;
    bottom: 0px;
    left: 55px;
}

#test .buttons a {
    display: block;
    width: 24px;
    height: 22px;
    text-align: center;
    line-height: 20px;
    color: white;
    font-size: 12px;
    font-weight: bold;
    text-decoration: none;
    background: black;
    margin-left: 2px;
    border-radius: 5px;
    opacity: 0.5;
    float: left;
}

#test .buttons a:hover {
    opacity: 1.0;
    color: yellow;
}

#test .buttons a.active {
    background: white;
    color: black;
    opacity: 1.0;
}

/* left/right arrow buttons: */

#test .nav {
    position: absolute;
    width: 100%;
    height: 50px;
    bottom: 0px;
}

#test .nav a {
    font-size: 36px;
    text-decoration: none;
    color: white;
    display: block;
    width: 50px;
    text-align: center;
    height: 50px;
    position: absolute;
    overflow: hidden;
}

#test .nav a:hover {
    color: yellow;
}

#test .nav a.prev {
    left: 1%;
}

#test .nav a.next {
    right: 1%;
}

example.js

jQuery(document).ready(function() {
    
    var slideshow = $('#test').Slideshow({
        slides: '#test div.slide',
        buttons: '#test div.buttons',
        prev: '#test a.prev',
        next: '#test a.next'
    });
    
    // example demonstrating a custom play/pause control:
    
    var pauseButton = $('#test div.toggle');
    
    pauseButton.click(function() {
        slideshow.toggle();
        pauseButton.text(slideshow.playing() ? '>' : '||');
        return false;
    });
});

jquery.slideshow.js

/**
 * jQuery Slideshow plugin
 * (responsive version with CSS3 optimized animation)
 *
 * author:  Rasmus Schultz <rasmus@mindplay.dk>
 * license: LGPL <http://www.gnu.org/licenses/lgpl-3.0.txt>
 *
 * This plugin creates a panning slideshow, optionally with left/right controls
 * and direct access to the individual slides via (numbered) index-buttons.
 *
 * No CSS is required, and there is no dependencies on any particular class-names,
 * element-types or element hierarchy - you can use whatever you want for slides,
 * containers, buttons, etc.
 *
 *
 * USAGE
 * =====
 *
 * Width and height options are not required - by default, the plugin picks up
 * the inner width/height of the slideshow container, so you can define that
 * using CSS, if you like.
 *
 * The slides must reside in a container, but it doesn't have to be the element
 * you applied the slideshow to - for example, if that element is a wrapper with
 * a background, you can use the "container" option to specify the actual container.
 *
 * You can specify the delay for individual slides, by adding a data-delay attribute
 * to the individual slide elements, specifying the time in seconds (decimals allowed.)
 *
 * If a container for index-buttons is specified (using the "buttons" option),
 * the plugin will generate an index-button for each slide; you can override the
 * default button-creation method using the "createButton" callback-option.
 *
 * The plugin does not generate the next/previous buttons - you can use the "next"
 * and "prev" options to apply event-handlers to your existing buttons/elements.
 *
 * Basic options: (all optional, except for "slides")
 *
 *   slides           selector or set of individual slides (required)
 *   container        overrides the slide container element (defaults to this)
 *   width            width in pixels (defaults to container's inner width)
 *   height           height in pixels (defaults to container's inner height)
 *
 * Animation options: (all optional)
 *
 *   easing           jQuery animation easing algorithm (defaults to "swing")
 *   speed            animation speed (in seconds - decimal allowed, default = 1.0)
 *   delay            delay between slides (in seconds - decimal allowed, default = 3.0)
 *                    (override using data-delay attribute on individual slides.)
 *
 * Navigation options: (all optional)
 *
 *   next             element for "next" button (by default, no next-button)
 *   prev             element for "previous" button (by deafult, no previous-button)
 *   buttons          container element for index-buttons (by default, no buttons)
 *   active           class-name for active index-button (defaults to "active")
 *   createButton     callback: function($slide,index)
 *                    creates an index button for a slide
 *                    (by default, an <a>-tag with a number is created)
 *
 * Public API:
 *
 *   You can control the plugin from your code - for example, to stop a slideshow:
 *
 *     $('#my-slideshow').Slideshow().stop();
 *
 *   The following public methods are available:
 *
 *     stop()         pause the animation
 *     start()        resume the animation
 *     toggle()       toggle the animation (start or stop)
 *     playing()      returns true if animation is running (otherwise false)
 *     next()         advance to next slide
 *     prev()         rewind to previous slide
 *     goto(index)    go to a specific slide (uses a 0-based index)
 *
 */
(function($) {

    /* https://gist.github.com/jonraasch/373874 */
    function supports_transitions() {
        var thisBody = document.body || document.documentElement,
            thisStyle = thisBody.style;
        return thisStyle.transition !== undefined || thisStyle.WebkitTransition !== undefined || thisStyle.MozTransition !== undefined || thisStyle.MsTransition !== undefined || thisStyle.OTransition !== undefined;
    }
    
    function Slideshow(el, options) {

        var
            $el = $(options.container || el),                 // slideshow container element
            $slides = $(options.slides),                      // list of slides
            $buttons = null,                                  // index buttons
            _delay = [],                                      // delay in milliseconds (for each slide)
            _easing = options.easing || 'swing',              // easing mode (for animation)
            _speed = parseFloat(options.speed || 1)*1000,     // speed (animation time)
            _timer = null,                                    // timer handle (for delay between slides)
            _blocked = false,                                 // user interface blocking (during animation)
            _resume = null,                                   // callback-function (when unblocking interface)
            _active = options.active || 'active',             // active class-name (for index buttons)
            _count = $slides.length,                          // number of slides
            _index = 0;                                       // current slide index
        
        var LEFT = '-100%',                                   // left position (CSS/animation)
            RIGHT = '100%',                                   // right position (CSS/animation)
            CENTER = '0%';                                    // center position (CSS/animation)

        var _slide = function (el, from, to, then) {
            $(el).css('left', from).animate(
                { left: to },
                _speed,
                _easing,
                then
            );
        };
        
        if (supports_transitions()) {
            // optimized slide function using CSS3 transitions:
            _slide = function (el, from, to, then) {
                $(el).css('transition', '0s').css('left', from);
                window.setTimeout(function() {
                    $(el).css('transition', 'left ' + _speed + 'ms ease').css('left', to);
                    window.setTimeout(function () {
                        then.apply(el);
                    }, _speed + 100);
                }, 20);
            };
        }
        
        $el.css('position', 'relative');

        $slides.each(function(i) {
            $(this).css({
                position: 'absolute',
                left: CENTER
            }).toggle(i==0);
            _delay[i] = parseFloat($(this).attr('data-delay') || options.delay || 3) * 1000;
        });

        if (options.buttons) {
            var create = options.createButton || _createButton;

            var $ct = $(options.buttons);

            $slides.each(function(i) {
                $ct.append(
                    $(create(this, i+1))
                        .click(function() { _goto(i); return false; })
                );
            });

            $buttons = $ct.children();
            $buttons.eq(_index).addClass(_active);
        }

        function _createButton(el, i) {
            return $(document.createElement('a'))
                .attr('href', '#')
                .text(i);
        }
        
        function _start() {
            _stop(); // clear any previous timeout
            _timer = window.setTimeout(_next, _delay[_index]);
        }

        function _stop() {
            window.clearTimeout(_timer);
            _timer = null;
        }

        function _playing() {
            return !(_timer == null);
        }

        function _toggle() {
            _playing() ? _stop() : _start();
            return _playing();
        }

        function _goto(index, direction) {
            if (_blocked) {
                // postpone this method-call until user interface is unblocked:
                _resume = function() {
                    _goto(index, direction);
                };
                return;
            }

            if (index == _index) return;

            window.clearTimeout(_timer); // clear timer

            _blocked = true;

            if (direction === undefined) {
                direction = index > _index;
            }

            // remove previous slide:

            _slide($slides.eq(_index).show(), CENTER, direction ? LEFT : RIGHT, function() {
                $(this).hide(); // hide the slide
                if (_timer) { _start(); } // resume playback
            });

            // display next slide:

            _slide($slides.eq(index).show(), direction ? RIGHT : LEFT, CENTER, function() {
                _blocked = false; // unblock user inteface
                if (_resume) {
                    _resume();
                    _resume = null;
                }
            });

            // update buttons:

            if ($buttons) {
                $buttons.eq(_index).removeClass(_active);
                $buttons.eq(index).addClass(_active);
            }

            // switch index:

            _index = index;
        }

        function _prev() {
            if (_blocked) {
                _resume = _prev;
                return;
            }
            _goto(_index == 0 ? _count-1 : _index-1, false);
        }

        function _next() {
            if (_blocked) {
                _resume = _next;
                return;
            }
            _goto((_index+1) % _count, true);
        }

        _start();

        if (options.prev) {
            $(options.prev).click(function(){ _prev(); return false; });
        }

        if (options.next) {
            $(options.next).click(function(){ _next(); return false; });
        }

        $.extend(this, {
            start: _start,
            stop: _stop,
            toggle: _toggle,
            playing: _playing,
            next: _next,
            prev: _prev,
            goto: _goto
        });

    }

    $.fn.Slideshow = function(options) {
        if (options === undefined) {
            return $(this).data('Slideshow');
        } else {
            var inst = new Slideshow(this, options);
            $(this).data('Slideshow', inst);
            return inst;
        }
    };

})(jQuery);

Previous version (not responsive, not CSS3 optimized)

Example (jsFiddle)