Recently, a friend of mine had a puzzle for me. It was one of the kind with the small playing field and the different-shaped pieces that are always in the way of moving that one piece to that other corner. I failed to do it by hand (haven't tried hard, though, just about half a boring lecture), but Haskell could do it for me in no time. Well, not no, but only a few otherwise boring hours, complete with ASCII-Art output etc.
As I'm currently tutoring students in a computer science class that uses Haskell, I was asked to publish the code. Thus I documented it using literate programming and LaTeX, so if you are interested, have a look at the PDF-Output or the code itself. The text is German, but the code should qualify as English.