The GHC library documentation at http://www.haskell.org/ghc/docs/latest/set/book-hslibs.html seems to have a lot missing:
* certain modules such as MonadError
There isn't any documentation for these Monad libraries that I'm aware of. Of course when HaskellDoc is up and running we'll have auto-generated documentation, but until then...
* the 'std' category * the Prelude
'std' just contains the Prelude and standard libraries, and a bunch of GHC-specific stuff that isn't intended for external consumption. The Prelude and standard libraries are documented in the report and library report respectively (and GHC is pretty ruthless about not exporting extra stuff from these libraries, so the Haskell 98 documentation should be accurate). When we switch over to the new library scheme and get HaskellDoc going, we'll be able to do a much better job here. Cheers, Simon