I've created a small wiki web site using ASP.NET and SQL Server. Code for this project is still a work in progress but it is freely available if you are interested on it.

You can visit this wiki web site at:
http://65.26.142.184/dotwiki/homepage.aspx

Be aware that this is still a work in progress that I created just for kicks while I am still learning ASP.NET. If you need a professional wiki software, make sure that you check Steven Black's wiki software.