The JavaAI Gaming Engine is a collection of games that allow easy integration, testing, and competition of AIs. The games that are supported: Hex and Ataxx, and in the future: TicTacToe, Chess, Checkers, Rock-Paper-Scissors, and more.
ArgosFields is a Java/SWT port of famous turn-based stategy game Crimson Fields(http://crimson.seul.org/). Unlike the original game, it will provide full network support, but lack AI opponent(for now at least).