If you're looking for a great Wiki implementation for ASP.NET, with a good user base and a whole lot of neat features to build on, look no more. David Ornstein has jumped through all the legal hoops, dotted all the i's, crossed all the t's, and has finally been allowed to release his FlexWiki software as shared source. This joins the previous WiX and WTL projects that have moved from Microsoft to SourceForge, for all you journalists keeping track :-)
I've been a happy user of David's previous versions of FlexWiki, both internally and on Channel 9, and now there's even more cool features to look forward to - like WikiTalk:
WikiTalk enables content contributors to access .NET framework objects for dynamic content while working within the traditional Wiki environment and it allows .NET developers to easily expose rich dynamic functionality to writers of Wiki content
Anyone who's remotely interested in wikis or collaborative software should check it out - or come back in a month or two after the community's had a chance to bash it around a bit and create even more wonderful things from it. Big, big thanks to David for hanging in there and making this happen!