Freedoom is a project to create a free software/open source Doom 2 IWAD file. Combined with the free source code, this results in a complete Doom-based game. All material in the Freedoom project is released under the modified BSD license, so other projects may reuse any of the Freedoom material for their own purposes as they wish. In fact, this is a secondary goal of the project.
The Battle for Wesnoth is a Free, turn-based tactical strategy game with a high fantasy theme, featuring both single-player, and online/hotseat multiplayer combat. It's packaged in PortableApps.com Format so it can easily integrate with the PortableApps.com Platform. And it's open source and completely free
Moodle is a Course Management System (CMS), also known as a Learning Management System (LMS) or a Virtual Learning Environment (VLE). It is a Free web application that educators can use to create effective online learning sites.
Tux Paint is a free, award-winning drawing program for children ages 3 to 12. It combines an easy-to-use interface, fun sound effects, and an encouraging cartoon mascot who guides children as they use the program. Kids are presented with a blank canvas and a variety of drawing tools to help them be creative.
Scorched 3D is a modernization of the classic DOS game Scorched Earth ("The Mother Of All Games"). It incorporates a lively three dimensional landscape that includes animated jets, naval vessels, water, and even birds, in addition to detailed tanks and projectiles. Other enhancements include LAN and Internet play and music.