Software Recommendation

Hi!
I am in need of some suggestion on what software to use:

I am working on a site that is going to require a client login. The login will allow a the client to upload and download file from the server via the browser. The administrator need to be able to post files into any client folder. An email to notify the client of new file to download and one to the admin when the client uploads would be nice.

Unix (shared)Server

I have found a lot of cgi script that do most, but not all features listed above. Does anyone have any recommendations?

Thanks for the help!
Rob