１、AspnetUpload
地址：http://www.aspnetupload.net/
最早接触的上传控件。带进度条，能与系统自带的InputFile控件共用。不过是收费的,而且对Firefox支持较差。最新版本是2.3
2、FancyUpload - Swiff meets Ajax (v2.0)（开源）
地址：http://digitarald.de/project/fancyupload/
Falsh上传,Ajax技术，还不错。
3、SWFUpload（开源）
利用JavaScript/Flash技术,非常成熟，跨平台,支持大多数浏览器。
4、这里再提供一个完整的源代码（来自CodeProject）
地址：http://www.codeproject.com/KB/aspnet/FlashUpload.aspx
Multiple File Upload With Progress Bar Using Flash and ASP.NET
也可以从这里下载
邀月补充：
5、 Ajax Uploader
ASP.NET File Upload like GMail(像Gmail那样上传文件，听名字就有点吸引人)
Ajax Uploader is an easy to use, hi-performance File Upload Control which allows you to upload files to web server without refreshing the page.
It allows you select and upload multiple files and cancel running uploads, add new files during uploading.
Ajax Uploader allows you to upload large files to a server with the low server memory consumption. The look and feel of file upload controls can be customized to seamlessly blend into your website design.
6、ComponentArt UI Framework 2009.2 for .NET 的Upload组件
官方网站http://www.componentart.com/
这个就不用说了！ 演示地址
http://aspnetajax.componentart.com/control-specific/upload/features/core_features/webform1.aspx