Flippi is a rather minimal Wiki clone written in Haskell. It's been dormant a fair while - originally I wrote it for purely personal purposes, and I have to confess to having let it bitrot somewhat. However, there's been some minor interest once in a while so I figure I should keep this page up even if I'm not maintaining it!
I also produced a version that I never quite released properly featuring an interesting static plugin system - this did see some use by others for prototyping purposes, and if I'm prodded enough I could be convinced to dig up whatever remnants of the code I have, bash it into a form that builds okay and release.
Current versions can be found on HackageDB under a BSD license: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Flippi . At time of writing the most recent version builds on the current version of GHC (6.8.3), unlike the versions linked below.
NOTE: Where both are provided, the zip archive contains DOS-formatted data files and README, the tar.gz contains unix-formatted files. All distributions are BSD-licensed.