css3 menu effect - see in action - http://jsfiddle.net/EwFHY/15/

fiddle.css

/* New navigation */

/* Some stylesheet reset */
 #cssmenu > ul {
    list-style: none;
    /* margin: -95px 0 0 0;*/
    padding: 0;
    line-height: 1;
    float: left;
    display:inline;
}
/* The container */
 #cssmenu > ul {
    display: block;
    position: relative;
    width: 90px;
    -webkit-transform-style: preserve-3d;
    -webkit-transform: rotateZ(2deg);
    filter: progid:DXImageTransform.Microsoft.BasicImage(rotation=2);
    -webkit-transition: all 0.5s ease-in-out;
    transition: all 0.5s ease-in-out;
    -webkit-backface-visibility: hidden;
    /* this will add an antiallias */
}
#cssmenu > ul:hover {
    display: block;
    position: relative;
    width: 90px;
    -webkit-transform: rotate(-15deg);
    -moz-transform: rotate(-15deg);
    -o-transform:rotate(-15deg);
    filter: progid:DXImageTransform.Microsoft.BasicImage(rotation=2);
}
/* The list elements which contain the links */
 #cssmenu > ul li {
    display: block;
    position: relative;
    margin: 0;
    padding: 0;
    width: 90px;
}
#cssmenu > ul li ul li, #cssmenu > ul li ul li a, #cssmenu > ul >li:hover, #cssmenu > ul >li:hover > a, #cssmenu > ul >li > a:hover {
    width:610px;
}
/* General link styling */
 #cssmenu > ul li a {
    /* Layout */
    display: block;
    position: relative;
    margin: 0;
    padding: 8px 20px;
    width: 90px;
    /* Typography */
    font-family:"Myriad Pro", "Trebuchet MS", sans-serif;
    /* letter-spacing: .05em;*/
    color: #939598;
    text-decoration: none;
    text-transform: lowercase;
    font-size: 13px;
    font-weight: 300;
    border-top-left-radius: 20px;
    border-bottom-left-radius: 20px;
    /* Background & effects */
}
/* The hover state of the menu/submenu links */
 #cssmenu > ul li.home>a:hover, #cssmenu > ul li.home:hover>a {
    color: #fff;
    background: #a2d062;
    background: -webkit-linear-gradient(bottom, #6e9b31, #a2d062);
    background: -ms-linear-gradient(bottom, #6e9b31, #a2d062);
    background: -moz-linear-gradient(bottom, #6e9b31, #a2d062);
    background: -o-linear-gradient(bottom, #6e9b31, #a2d062);
    border-color: transparent;
    -webkit-transition: all 0.2s linear;
    -moz-transition: all 0.2s linear;
    -o-transition: all 0.2s linear;
    transition: all 0.2s linear;
}
#cssmenu > ul li.productsrev>a:hover, #cssmenu > ul li.productsrev:hover>a {
    color: #fff;
    background: #61c46e;
    background: -webkit-linear-gradient(bottom, #2b8a39, #61c46e);
    background: -ms-linear-gradient(bottom, #2b8a39, #61c46e);
    background: -moz-linear-gradient(bottom, #2b8a39, #61c46e);
    background: -o-linear-gradient(bottom, #2b8a39, #61c46e);
    border-color: transparent;
    -webkit-transition: all 0.2s linear;
    -moz-transition: all 0.2s linear;
    -o-transition: all 0.2s linear;
    transition: all 0.2s linear;
}
#cssmenu > ul li.about>a:hover, #cssmenu > ul li.about:hover>a {
    color: #fff;
    background: #459cc7;
    background: -webkit-linear-gradient(bottom, #025e8e, #459cc7);
    background: -ms-linear-gradient(bottom, #025e8e, #459cc7);
    background: -moz-linear-gradient(bottom, #025e8e, #459cc7);
    background: -o-linear-gradient(bottom, #025e8e, #459cc7);
    border-color: transparent;
    -webkit-transition: all 0.2s linear;
    -moz-transition: all 0.2s linear;
    -o-transition: all 0.2s linear;
    transition: all 0.2s linear;
}
#cssmenu > ul li.customers>a:hover, #cssmenu > ul li.customers:hover>a {
    color: #fff;
    background: #2e6dab;
    background: -webkit-linear-gradient(bottom, #09427a, #2e6dab);
    background: -ms-linear-gradient(bottom, #09427a, #2e6dab);
    background: -moz-linear-gradient(bottom, #09427a, #2e6dab);
    background: -o-linear-gradient(bottom, #09427a, #2e6dab);
    border-color: transparent;
    -webkit-transition: all 0.2s linear;
    -moz-transition: all 0.2s linear;
    -o-transition: all 0.2s linear;
    transition: all 0.2s linear;
}
#cssmenu > ul li.contacts>a:hover, #cssmenu > ul li.contacts:hover>a {
    color: #fff;
    background: #6852a4;
    background: -webkit-linear-gradient(bottom, #3d2975, #6852a4);
    background: -ms-linear-gradient(bottom, #3d2975, #6852a4);
    background: -moz-linear-gradient(bottom, #3d2975, #6852a4);
    background: -o-linear-gradient(bottom, #3d2975, #6852a4);
    border-color: transparent;
    -webkit-transition: all 0.2s linear;
    -moz-transition: all 0.2s linear;
    -o-transition: all 0.2s linear;
    transition: all 0.2s linear;
}
/* THE SUBMENUS */
 #cssmenu > ul ul {
    position: absolute;
    left: 120px;
    top: -9999px;
    padding-left: 0px;
    padding-top: 40px;
    opacity: 0;
    z-index: 1;
}
#cssmenu > ul ul.bgsubproducts {
    background-image: url(http://dev.unnaturallygeisha.com/fellowrobots/wp-content/uploads/2013/02/square-gradient.png);
    background-repeat:no-repeat;
    overflow: visible;
    height: 200px;
    margin-top:-40px;
    margin-left: 0px;
    z-index:-100;
    -webkit-transition: opacity 1s;
    -moz-transition: opacity 1s;
    -o-transition: opacity 1s;
}
#cssmenu > ul ul.bgsubabout {
    background-image: url(http://dev.unnaturallygeisha.com/fellowrobots/wp-content/uploads/2013/02/square-gradient.png);
    background-repeat:no-repeat;
    overflow: visible;
    height: 200px;
    margin-top:-40px;
    margin-left: 0px;
    z-index:-100;
    -webkit-transition: opacity 1s;
    -moz-transition: opacity 1s;
    -o-transition: opacity 1s;
}
#cssmenu > ul ul.bgsubcustomers {
    background-image: url(http://dev.unnaturallygeisha.com/fellowrobots/wp-content/uploads/2013/02/square-gradient.png);
    background-repeat:no-repeat;
    overflow: visible;
    height: 200px;
    margin-top:-40px;
    margin-left: 0px;
    z-index:-100;
    -webkit-transition: opacity 1s;
    -moz-transition: opacity 1s;
    -o-transition: opacity 1s;
}
#cssmenu > ul ul li a {
    color: #5d6064;
    background: transparent;
    z-index:1000;
}
#cssmenu > ul ul li.subproducts:hover>a {
    color: #2b8a39;
    background: transparent;
}
.subproducts {
    z-index:1000;
}
#cssmenu > ul ul li.subabout:hover>a {
    color: #025e8e;
    background: transparent;
}
#cssmenu > ul ul li.subcustomers:hover>a {
    color: #09427a;
    background: transparent;
}
/* Showing the submenu when the user is hovering the parent link */
 #cssmenu > ul li:hover>ul {
    top: 30px;
    opacity: 1;
}

fiddle.html

<div id='cssmenu'>
    <ul>
        <li class='home'><a href="#" title="Link 1">home</a>

        </li>
        <li class='productsrev'> <a href="#" title="Link 3">products</a>

            <ul class="bgsubproducts">
                <li class='subproducts'><a href="#" title="Link 1">helo</a>

                </li>
            </ul>
        </li>
        <li class='about'><a href="#" title="Link 3">about</a>

            <ul class="bgsubproducts">
                <li class='subabout'><a href="#1" title="Link 1">what's a telepresence robot?</a>

                </li>
                <li class='subabout'><a href="#1" title="Link 1">our team</a>

                </li>
                <li class='subabout'><a href="#1" title="Link 1">our robots</a>

                </li>
                <li class='subabout'><a href="#1" title="Link 1">our partners</a>

                </li>
            </ul>
        </li>
        <li class='customers'><a href="#4" title="Link 4">customers</a>

            <ul class="bgsubproducts">
                <li class='subcustomers'><a href="#1" title="Link 1">driving control panel</a>

                </li>
                <li class='subcustomers'><a href="#1" title="Link 1">instructions</a>

                </li>
                <li class='subcustomers'><a href="#1" title="Link 1">&nbsp;&nbsp;&nbsp;&nbsp; setting up your robot</a>

                </li>
                <li class='subcustomers'><a href="#1" title="Link 1">&nbsp;&nbsp;&nbsp;&nbsp; driving instructions</a>

                </li>
            </ul>
        </li>
        <li class='contacts'><a href="#" title="Link 5">contacts</a>

        </li>
    </ul>
</div>

fiddle.manifest

name: css3 menu effect
description: pure css3 animated menu effect