Mindquarry is a web workspace CSCW tool based on Apache (with a Java application server) and Subversion for the server-side.

It includes team management, file sharing (with versioning, apparently), a “WYSIWYG”:Wikipedia:WYSIWYG Wiki editor and task management.

As far as I can tell, it uses WebDAV for file storage and item access, and has the great benefit of having native front-ends for all platforms.