Well we have a RedHat server running:
1. Moodle - Course Management
2. Elgg - Social Networking
3. Gallery2 - Photo Hosting
4. WordPressMU - Blog
5. Drupal - Website
6. Media Wiki - Wiki Site
All of the programs are FREE. There is fee for the server support for RedHat. But I could use Fedora or CentOS as the server software and those are free.