Here are some links I've dug up that might be useful.

Official Baseball Rules
I know I'm the only one that actually knows almost all of them including the obscure ones. This is the online version of the book I have, so if you're curious as to whether something has a rule against/allowing it, you can look here.

Baseball Rules Quiz
Once you think you know all the rules... try this. It's quite obscure a lot of the time and even I only get about 70-80% right.

Webball
Want to figure out the proper mechanics of swinging? How to pitch? Some drills to run? It's a great site for teaching baseball technique and procedures. I highly recommend you all take a look.