Edge Online has a post full of great links surrounding the Half-Life 2 Rube Goldberg videos. Heck, if you just want to watch these all day long, there's a thread here with links to dozens of them! The metric they measure these by is the length of the "Goldberg." Longer, of course, means better.

There is an ongoing challenge to produce the longest running Goldberg, although the top ten list is really out of date. Posters to the thread are claiming to have Goldbergs that run as long as 2 minutes!