The famous "Jitbit ASP.NET forum" - a .NET message board app. Easily integrated into existing .NET-websites (both design and authentication). Free edition available. Source codes license available.
"Jitbit's AspNetForum is ridiculously fast" - Scott Hanselman, blogger, writer, Microsoft Web Team architect.
The Forum software is built with the C# language, you can have the source code version if you want. The Forum is compatible with MS SQL Server, MySQL and even Access database engines.
Easily customize the look-and-feel for your forum, configure the forum to accept your existing users (via ASP.NET authentication or built-in Auth-API"). More info
Create user-groups, assign posting and reading permissions to users, moderate messages, activate user-accounts by email and more.
Jitbit's ASP.NET forum lets users sign in with their Twitter and Facebook accounts. Just specify your Twitter/Facebook "API key" in the settings and it works out of the box! OpenID is also supported - log in with a Google/Yahoo/<you-name-it> account.
Possible Windows-integrated authentication - integrate this message board with your existing Active Directory users catalog.
Jitbit Forum (formerly known as "Jitbit AspNetForum") is an ASP.NET forum/discussion board software. Download and add an forum to your ASP.NET-based site in seconds - from the creators of Jitbit Help Desk System
Our forum easily integrates into existing ASP.NET-based websites, optionally offering a "single-sign-on" functionality for your existing users.
Our forum comes with English, Spanish, Portuguese, German, Swedish, Turkish, Danish, Hebrew, Dutch, Italian, French, Arabic, Russian, Czech, Hindi and Chinese Traditional translations. Other languages can be easily added using ASP.NET resources.