For the past month I've been working on implementing a chess rules engine in Java. I started it just to improve my TDD skills, but when I finished the engine it only seemed logical to create a way to actually use the code to do something a little more fun than running unit tests.
So I decided to write an Ajax interface for the chess engine. Today I finished the first iteration (human vs. human on the same computer), and it is available as a preview at:
Ajax chess on Brasee.com Games
The source code is also available at http://code.google.com/p/java-chess-web.
I still don't have the web app checked in yet, I'll work on getting that up in the next week or two when I get it cleaned up and generalized.
For the next iteration, I'm planning on adding a basic lobby system and making this game playable between people over the web. Yeah I know, big goals for a single iteration in a spare time project, LOL. After that, if I'm feeling really adventurous, I might try to implement some basic chess artificial intelligance. I'll no doubt have to brush up on my min-maxing and alpha-beta pruning, and figure out the best way to implement it in Java.