AjaxFileUpload 90% or source: http://www.phpletter.com/Our-Projects/AjaxFileUpload/

dimsum-global-functions.js

( function($) {

	$.fn.uploadFile = function(options) {

		ajaxFileUpload(this.filter(':file'), options);
		return this;
	};

	function ajaxFileUpload(elements, s) {

		s = $.extend({}, $.ajaxSettings, s);

		var id = new Date().getTime(),
			form = createUploadForm(id, elements, s.url, s.data),
			frame = createUploadIframe(id, s.secureuri);

		var frameId = 'jUploadFrame' + id;

		// Watch for a new set of requests
		if (s.global && !$.active++) {
			$.event.trigger("ajaxStart");
		}
		// Create the request object
		var requestDone = false, xml = {};

		if (s.global)
			$.event.trigger("ajaxSend", [xml, s]);

		// Wait for a response to come back
		var uploadCallback = function(isTimeout) {
			var io = document.getElementById(frameId);
			try {
				if (io.contentWindow) {
					xml.responseText = io.contentWindow.document.body ? io.contentWindow.document.body.innerHTML : null;
					xml.responseXML = io.contentWindow.document.XMLDocument ? io.contentWindow.document.XMLDocument : io.contentWindow.document;

				} else if (io.contentDocument) {
					xml.responseText = io.contentDocument.document.body ? io.contentDocument.document.body.innerHTML : null;
					xml.responseXML = io.contentDocument.document.XMLDocument ? io.contentDocument.document.XMLDocument : io.contentDocument.document;
				}
			} catch(e) {
				handleError(s, xml, null, e);
			}
			if (xml || isTimeout == "timeout") {
				requestDone = true;
				var status;
				try {
					status = isTimeout != "timeout" ? "success" : "error";
					// Make sure that the request was successful or not modified
					if (status != "error") {
						// process the data (runs the xml through httpData regardless of callback)
						var data = uploadHttpData(xml, s.dataType);
						// If a local callback was specified, fire it and pass it the data
						if (s.success)
							s.success(data, status);

						// Fire the global callback
						if (s.global)
							$.event.trigger("ajaxSuccess", [xml, s]);
					} else
						handleError(s, xml, status);
				} catch(e) {
					status = "error";
					handleError(s, xml, status, e);
				}

				// The request was completed
				if (s.global)
					$.event.trigger("ajaxComplete", [xml, s]);

				// Handle the global AJAX counter
				if (s.global && !--$.active)
					$.event.trigger("ajaxStop");

				// Process result
				if (s.complete)
					s.complete(xml, status);

				$(io).off();

				setTimeout(function() {
					try {
						$(io).remove();
						$(form).remove();
					} catch(e) {
						handleError(s, xml, null, e);
					}
				}, 100)

				xml = null;
			}
		};
		// Timeout checker
		if (s.timeout > 0) {
			setTimeout(function() {
				// Check to see if the request is still happening
				if (!requestDone)
					uploadCallback("timeout");
			}, s.timeout);
		}
		frame.load(uploadCallback);
		try {
			form.submit();
		} catch(e) {
			handleError(s, xml, null, e);
		}
	}

	function createUploadIframe(id, uri) {
		//create frame
		var iframeMarkup = [
				'<iframe id="jUploadFrame', id, '" name="jUploadFrame', id, '" style="position:absolute; top:-9999px; left:-9999px" ', getSrc(uri), ' />'
			].join('');

		return $(iframeMarkup).appendTo(document.body);
	}

	function getSrc(uri) {
		if (window.ActiveXObject) {
			if ( typeof uri == 'boolean') {
				return ' src="javascript:false" ';
			} else if ( typeof uri == 'string') {
				return ' src="'+uri+'" ';
			}
		}
		return '';
	}

	function createUploadForm(id, elements, url, data) {
		//create form
		var fileId = 'jUploadFile' + id,
			formMarkup = [
			'<form style="position: absolute;top: -1200px;left: -1200px;" action="', url, '" method="POST" name="jUploadForm', id, '" id="jUploadForm', id, '" enctype="multipart/form-data" encoding="multipart/form-data" target="jUploadFrame', id, '"></form>'
			].join(''),
			form = $(formMarkup);
		$.each(data || {}, function(k, v){
			$('<input type="hidden" name="'+ k + '" />').val(v).appendTo(form);
		});

		elements.each(function(i){
			var source = $(this), substitute = source.clone(true, true);

			source.attr('id', fileId + '_' + i);
			substitute.insertBefore(source);
			source.appendTo(form);
		});

		return form.appendTo('body');
	}

	function uploadHttpData(r, type) {
		var data = !type, type = type.toLowerCase();
		data = type == "xml" || data ? r.responseXML : r.responseText;

		switch (type) {
			case 'script':
				// If the type is "script", eval it in global context
				$.globalEval(data);
				break;
			case 'json':
				// Get the JavaScript object, if JSON is used.
				eval("data = " + data);
				break;
			case 'html':
				// evaluate scripts within html
				$("<div>").html(data).evalScripts();
				break;
		}
		return data;
	}

	function handleError(s, xhr, status, e) {
		// If a local callback was specified, fire it
		if (s.error)
			s.error(xhr, status, e);

		// Fire the global callback
		/* INCOMPATIBLE!!! Modern jQuery 1.5+ expects xhr to be an jqXHR object.
		 if ( s.global )
		 $.event.trigger( "ajaxError", [xhr, s, e] );
		 */
	}

}(jQuery));