Sodaplay and Sodarace
Someone called me to watch the end of a segment on BBC's Click Online. Sodaplay is a site that lets one create mechanical objects, and then simulate them. Sodarace takes the process further.
I have just discovered these sites, and, although I'm fairly busy at the moment, I'll try to learn more about them, and update you on what I find out, but what I've seen so far seems intriguing.