Here's a great website for all you technical guys...
Mattias Wandel is a young fellow that has been making complex machines and toys etc. since he was a teenager. You'll probably be amazed at some of the things he does. There's lots of detailed documentation, plans, and video demonstrations of things he and some of his friends create.
One thing I just posted elsewhere was a video of his wooden crossbow.
Watch the CrossBow shooting marbles through 1/2" plywood.