Besides GHCi this is my reference shelf
- Prelude source and http://www.haskell.org/onlinereport/haskell2010/haskellch9.h...
- 2010, 98 reports (which are very readable, unstiff/undry docs
- use google to search stackoverflow/questions/tagged/haskell
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:
(on about the 17th google page for "haskell cheat"
also symbolhound works pretty well for searching stackoverflow for symbolic operator/function names, e.g. haskell <$>