I think haskell has more orthogonal language features than, say, java, where everything holds together pretty well but you can't un-congeal features and use by themselves.

Besides GHCi this is my reference shelf

- http://www.cl.cam.ac.uk/~ns441/files/thips.pdf

- http://acm.wustl.edu/functional/hs-breads.php

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- http://www.haskell.org/hoogle/

- http://www.haskell.org/haskellwiki/Typeclassopedia

- Prelude source and http://www.haskell.org/onlinereport/haskell2010/haskellch9.h...

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- 2010, 98 reports (which are very readable, unstiff/undry docs

- use google to search stackoverflow/questions/tagged/haskell

- http://ezyang.com/haskell.html

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Books: Hudak's "School of Music" (tho I'm not sure how interesting it is unless you know how to read/play music), and the 3 books by Hutton, Thompson, and Bird. It has been remarked that the "gentle Intro" is actually kind of harsh, the Hutton and Thompson books really are gentle intro's:

http://www.haskell.org/tutorial/

http://haskell.cs.yale.edu/euterpea-2/haskell-school-of-musi...

http://www.amazon.com/Pearls-Functional-Algorithm-Design-Ric...