Wow, Heroscape (official site, fan site) is an amazing toy and a rather fun game. It's pretty much a miniatures game, which I usually find appealing, but not actually enjoyable. This succeeds at being both rich in gameplay and simple. The terrain and corresponding rules are outstanding. Plus, it is an amazing amount of toy bits. It's a blast. There's something very geeky but very entertaining about a game coming down to a battle between a Viking and a robot.
I've written a web-based unit card creator for aiding in the creation of new units.
Updated: See my review of Heroscape and some unit creator improvements.