Microsoft has been started beta version of CodePlex, another open source project portal after gotdotnet; but that one supported with aspx and team foundation server.
Here is the discription of site with their own word : “CodePlex is an online software development environment for open and shared source developers to create, host and manage projects throughout the project lifecycle. It has been written from the ground up in C# using .NET 2.0 technology with Team Foundation Server on the back end. CodePlex is open to the public free of charge.”
Yo can visit web site at http://www.codeplex.com