Have you tried Coalton? It's a Common Lisp library that adds Haskell-esque (or near-Haskell) type wonders, and which smoothly interoperates with your Common Lisp code.

Your comment is great though, consider me convinced. I've done a bit of messing with Lisp, but really would like to try write something in Haskell, or slog through a book or two, some day.