Pupload is a jQuery implementation of a multi-upload widget. If uses either a Falsh component, html5, Gears, Silverlight or Yahoo BrowserPlus in order to provide a strong and highly reliable multi-upload system.
http://www.ronniesan.com/articles/jquery-multiple-file-upload.php
This link is now broken.
about:
Neat and useful jquery plugin which allows you to change any element into a single or multiple file upload tool. The plugin uses a mix of JQuery, Flash, and a backend upload script to send files from the local computer to the website server.
The Multiple File Upload Plugin (jQuery.MultiFile) is a non-obstrusive plugin for the jQuery Javascript library that helps users easily select multiple files for upload quickly and easily whilst also providing some basic validation functionality to help developers idenfity simple errors, without having to submit the form (ie.: upload files).