I have to take my words back in terms of edgy development on Mac, in respect to Haskell. Basically thru macports system it is possible to install Haskell in version 6.6.1 or even development version 6.7 witch is really edgy now. And it is as easy as on Linux:
sudo port install ghc
or ghc-devel for 6.7 version. I was really surprised when I find out that really cool package hoc. It was created for Haskell version 6.1, of course it works perfectly for my needs – you can use it with the newer version but you can only use procedures that existed in version 6.6.1, but it means that sooner or later I will face problems. Any way, be aware that macports will additionally install ncurses-5.6, gmp-4.2.1, perl-5.8.8, readline-5.2, ghc-6.6.1. Do you see what I see Perl, what is this guy doing here. It reminds me this RoR installation - it installs PHP and actually uses it to do configuration tasks; how weird is that? By the way Instant Rails is the most common way to install RoR on windows.
Going back to main topic installation of all GHC dependencies will take a while, so be patient. If you never wrote anything in Haskell be sure to see if GHC is really the thing that you want. Basically majority of programs written for HUGS will not run on GHC and vice versa. It reminds me (again) about scheme, if you use guile your programs will probably not work on MIT/GNU Scheme or DrScheme. You will have to modify your code. Oh, well - life is taft.
But again don't you feel that it is sad. You program in a language that is understood only by a few, and you are unable to share it with all of those who understand it?