JPentago is a Java implementation of the original Pentago game. Grab the code from the JPentago google code subversion site and get started.
Tanks 3D is a multiplayer tank game where you're pitted against an enemy in rough terrain, and you take turns firing artillery on one another. Similiar to the classic Scorched Earth, but with a 3rd dimension. Grab the code from the Tanks3D Source Forge CVS repository and get started.
Trail of Tears is a persistent world online RPG. The game will contain elements of the old west blended with a twisted sense of humor.
XpandO - (description later).