The following programs installed with GHC (specifically, using the Mac OS X installer, though I suspect this applies to all platforms) do not have manpages:

• ghc-pkg
• ghci (Technically, its manpage is the same as ghc's, but there's no ghci.1 symlink to ghc.1, so man ghci fails to find anything.)
• haddock
• hp2ps
• hpc
• hsc2hs
• runghc
• runhaskell

I think that's all of them.

I realize that not all of these programs (e.g., haddock) are truly part of GHC, but the ones that are still need manpages. If the problem is that writing *roff is hard, and you don't mind mooching off other languages, might I refer you to POD/pod2man?