Multiple File Upload options for a c# .net web based project

I am looking for viable solutions to give a GMail like multiple file upload capability. A couple of things that need to take into consideration is the easy of integration and compatibility. We need to add this feature to our application to improve the end users ability to upload multiple files at once. This is for a business product so we need to be able to use it in several applications.
We do not mind paying for it but if the cost is two high we will make our own. If we end up going the manual route to make a application which platform would be suggested. I am thinking either flash or java.

Any input or experience with this is appreciated, please don't just submit google search results as I can do that myself.

Thanks