Client Side Upload Application

I am interested in a web-based client side application which will allow the user to select a directory on his/her machine.? The application will then recurse through the files and perform minor test, such as is it a pdf file or not? and then upload the complete directory to a server component.? The server component is? a very simple component to run on an IIS server.? The server will receive the data and place it in a pre-configured directory maintaining the client directory structure. This is a proto-type for a bigger project and I will be interested in some sort of a technology bake-off to include options such as an applet, an app that runs using Java webstart.? Also, I would be interested in a VB.NET or C#.NET thick client to do the same take.? Therefore, I will be interested in your input first and then we can choose one path and proceed with it.? I expect a second project to spin off based on the success of this project.