If your a fan of photoshop, or graphic design, or just plain bored on friday afternoons: I highly recommend checking out Layer Tennis. The game rules are simple:

1. Think Tennis but with photoshop
2. two opponents
3. fifteen minutes per volley 

Some of the best graphic designers and bloggers out in the world wide interwebs have been featured in this competition, lately it has evolved from just graphic deign to incorporate video and motion design elements as well.