I finally got round to building gtk2hs packages for Fedora Core 5
and they are available now from <http://haskell.org/fedora/>.
In addition to ghc641-gtk2hs-cairo there is also a "virtual"
ghc-gtk2hs package which should make upgrading smoother when the ghc
version changes: currently it just pulls in ghc641-gtk2hs.
Please report any problems here.
ps I'm going to submit this gtk2hs package to Fedora Extras.