To get a feel for what real world Haskell looks like, here are some examples from various popular Haskell projects.
Library code usually differs from application code: it is often highly structured, and documented with haddock, and can be rather optimised.
Code from popular Haskell applications:
Darcs, a revision control system (uses literate Haskell style)
Pugs, a perl6 implementation
Yi, a text editor
Conjure, a bittorrent client
DownNova, a file downloading program
cpphs, an implementation of the C preprocessor
GHC, a Haskell compiler
Djinn, a theorem prover
c2hs, a C to Haskell interface generator
Lambdabot, an IRC bot
hmp3, an curses mp3 player
Here is a list of other random code collected on this wiki, replacing CodeOnTheWiki. Contributors of code to the old area are encouraged to bring their code over here. This should only be done by the original author because anything on these pages is automatically licensed under the Simple Permissive License (HaskellWiki:Copyrights).
Prelude extensions: Simple things you've always wished were in the Prelude.
Gallery: Complete small programs.
Blow your mind: Short, useful, cool, magical examples, which should incite the reader's curiosity and (hopefully) lead him to a deeper understanding of advanced Haskell concepts.
NewMonads: Useful monads that are not in the main library.
PrincipalVariationSearch: Principal variation search