Developer Community Tools

Hi - I work for a large company and we are looking for some advice on building a new "Developer Portal". Our infrastructure is built on IIS and our standard DB cluster is MSSQL.

I'm wondering if there are any ASP.NET based community portal solutions which might speed up the development of this community? Pre-Existing, packaged tools?

Our goal is to have a secure login area with user based permissions for different areas of the site in addition to mail capabilities.

In the PHP world there are loads of these community style scripts, but haven't seen anything similar for non LAMP installs.

Has anyone ever come across such a thing? If so, would you mind sharing?

Thanks in advance.

David