Plupload
Multiple file upload utility using Flash, Silverlight, Google Gears, HTML5 or BrowserPlus!
3 Alternatives To Plupload
FancyUpload
digitarald:Harald K - Consultant & Contractor - FancyUpload - Swiff meets Ajax - Swiff meets Ajax for powerful and elegant uploads.
Fine Uploader
Javascript plugin tool to give your users a smooth experience when uploading files to your website.
Uploadify
Uploadify is a jQuery plugin that allows users to easily add multiple file upload functionality to their website.