Now I know why I kept all those Legos that I used to play with. This guy has come up with schematics for creating Lego Logic Gates:

A few people have designed boolean logic devices using LEGO pneumatics and gone on to develop fundamental computer devices such as full-adders and flip-flops. These have been discussed greatly on LUGNET. I had suspected that there would be a large number of logic devices using mechanic principals, but a search for mechanical logic devices didn't get many hits. I got one hit on mechanical logic detailing the use of rods to make logic gates. To my suprise I only came across two LEGO webpages that gave any details of mechanical logics gates. The first page, has details of a LEGO NOT gate. And the other page has photos of an AND gate. If you made any mechanical logic gates then please let me know!

He even has a diagram fror making a Flip Flop! Pictures are of course included... and they look pretty cool. I may have to do this for fun some time. Wow. I am a geek if I think this would be fun.