I've been enjoying Drupal for a couple of months now in a development environment, porting over my old PHP text-based code from my old site into modules that I can use in my new site. The Weboffice Portal module is actually in use on 4minds.com and is available to any user who is also a client of 4Minds Internet Group.

Clients will have a view into their projects to check on statuses, and will also be able to approve or reject estimates right inside their own interface while logged into the site.