Like programming? This is quite fun.

[Sean Raia]

I found a game a while back where you could program robots to fight other ones, the only problem was that it was very old and the website was abandoned years ago. Apparently, someone took up work on it again and its now back up!

The programming style is not at all logical (or perhaps too logical), but it is quite fun and i think a lot of people may get sort of hooked.

Heres the website:
http://botbattle.alwaysdata.net/

Enjoy!

[Mk.32]

There is also RoboCode which is a pretty fun JAVA robot programming game.
You make tanks that shot each other :D

http://robocode.sourceforge.net/

[Sean Raia]

That is quite fun, i have given it a shot a couple times. The real "awesome" awesome feature to the one i posted is the wide array of weapons and the fact that you can instantly battle bots from around the world, but the website is very bare.

[JesseK]

If you really like programming Java, you can suffer through this book:
http://www.javapuzzlers.com/

Found via one of my daily tech blogs:
http://vanillajava.blogspot.com/

I'll check out the game when I get home ;)

[DjMaddius]

Believe it or not, Facebook as puzzles for programming. They are very intense also.
http://www.facebook.com/careers/puzzles.php