As Clint writes on his blog, we have now Yesod, a Haskell web framework, packaged in Debian. Despite his humble choice of words, it was mostly his work, and it is quite some work, given that Yesod has a huge number of dependencies that were not yet packaged.
So if you want to use Yesod on Debian, and prefer pre-built libraries without dependency problems and clean installation/deinstallation with dpkg over having always latest and greatest, this should provide you with a solid base.
Have something to say? You can post a comment by sending an e-Mail to me at <mail@joachim-breitner.de>, and I will include it here.