This is a java applet called GuessHoo. It's a simple guessing game, replicating the classic MB board game called "Guess Who". My art work isn't as pretty as the board game, but maybe Rufio will take pity on me ;-)
Planeshift is a free MMORPG. The game engine is the brilliant open source CrystalSpace and the planeshift engine is also open source. The game itself is still in Alpha, but don't let that put you off. It really is very playable already and when it's finished it's going to be excellent.
I just read on linuX-Gamers that S2 Games have decided to make Savage free! This is undoubtedly to generate interest in the upcoming release of Savage 2, but it's still great news. Now you have no excuse not to take it for a spin.
You can only get the windows client from the Savage home page, but linuX gamers linked directly to the Linux files. I'm reproducing those links below.