If you've ever wondered at some of the seemingly arcane things you can do with the Haskell type system, take a look at the latest copy of The Monad Reader. There's an article in there called Type Level Instant Insanity that's the clearest introduction I've seen yet to leveraging the Haskell type checker for compile-time programs. Excellent work.

I've been meaning to do this for a long time now, glad to see I'm not the only crazy one. http://haskell.org/haskellwiki/Yhc/Javascript/Programmers_guide