I am looking for free / open or private forum software for asp.net. Most of the ones I found require PHP and MySql.
http://www.yetanotherforum.net/ - Another forum is a fairly popular package of forums based on ASP.NET.
You can try "Jitbit AspNetForum" http://www.jitbit.com/asp-net-forum/ We have used it for many years and they have a free evaluation version (fully functional). He also received a good review from Scott Hanselman here http://www.hanselman.com/blog/HanselmanForumsAspNetForumFromJitBit.aspx
Codeplex has a few: here
Chad Moran mentioned a good one, but I will contact the C # open source forum where I found it (simply because the website is familiar)
Another .net forum