About 2 months ago I was looking for a wiki platform for my day job (www.voler.com). I was looking for an ASP.net based WIKI, but was open to other platforms... Luckily I ran across ScrewTurn and was super impressed. It seems to be a very well organized project utilizing the latest ASP.net platform features, plus it was very easy to get setup and customize.
Originally I wasn't sure what we would use a WIKI for, but I knew I needed some sort of intranet/document repository for the various departments at Voler. It turns out the ScrewTurn is perfect as an Intranet platform.
Below are the top things that I like about ScrewTurn:
No DB required, it stores all articles (and previous version) as text files
Extensible modular platform, making it easy for others to build onto it
Support for single signon using Active Directory (someone is developing an extension for this)
Simple easy to understand framework (this means it's easy to customize)
go to http://www.screwturn.eu/Wiki.ashx for more info.