I'm not sure if something like this exists or not. I sure hope so.

I'm looking for a way for my employees and clients to share files through a Web interface.

The script would need to have good security options. Preferably, group-based. Where Client A could see all the files associated with their projects, but could not see Client B's project files. Employees could access anybody's files.

This script will be a Web site unto itself, so my options are wide open here. I can be PHP, ColdFusion, whatever. I'm even open to using something like Joomla or Drupal, if that's an easy option.

Any thoughts?