Real World Haskell by Bryan O'Sullivan, Don Stewart, and John Goerzen

[quesebifurcan (Fredrik Wallberg)]

A practical introduction to Haskell which is well worth a read for anyone curious about functional programming.

http://shop.oreilly.com/product/9780596514983.do (paperback)
http://book.realworldhaskell.org/read/ (read online)