File Upload with progress bar

AJAX toolkit has two controls: AsyncFileUpload (multiple files w/ progress bar) and AjaxFileUpload (single file)

http://www.asp.net/ajaxLibrary/AjaxControlToolkitSampleSite/AsyncFileUpload/AsyncFileUpload.aspx

Here's a File Upload with progress bar
http://www.codeproject.com/Articles/113418/ASP-NET-File-Upload-with-Progress-Bar

Here's a way to change the presentation (e.g., change button image) using jQuery
http://www.appelsiini.net/projects/filestyle