Suggested sources for learning Haskell:

* RealWorldHaskell - an online beta of the O'Reilly book, free to read and free to add comments
** Also available as a physical book as well.
* VitalHaskell - a very cool multimedia Haskell running over a jvm.
* HappsFramework - a web app construction kit entirely in Haskell. 
** ''If you can program anything in HappS you actually already learned Haskell.''
* http://www.zvon.org/other/haskell/Outputglobal/index.html is a nice online reference
* Once you start working with the language you'll need to learn DarcsRevisionControl and HackageHoogleCabal
* LearnYouaHaskellForGreatGood is a brilliant introduction to Haskell for total newbies.  
* And for more there is the great Haskell Wikibook.

What else?

See HaskellLanguage
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CategoryHaskell