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.
Since CodePlex is based on Team Foundation Server you can connect to the CodePlex site via the Team Client which will then display all projects for which you are a member.
You have to request approval to get a new project added to the site but they also state that if you create a gotdotnet project first, then your chances will be improved (assuming your gotdotnet project is active).
Word has it that Microsoft's current plan is to launch the final version of CodePlex at the Open Source Business Conference in London in late June.