CodePlex celebrates two years old. codeplex.com is the Microsoft community development site where open source projects are posted. Codeplex receives more than one million unique visitors per month and has more than 5,000 projects posted, according to Somasegar's WebLog: CodePlex celebrates its 2nd birthday!
CodePlex is built on Team Foundation Server (TFS). Specifically, seven TFS servers run more than 5,600 projects and cater to 12,000 project developers and 120,000 code check-ins.
Open source developers can use the Visual Studio Team Explorer client for free with CodePlex to get the full integrated development experience. CodePlex also supports a wide range of other source control clients such as TortoiseSVN and TeamPrise to give users more flexibility and cross-platform access.
You can download Team Explorer from Download: Visual Studio Team System 2008 Team Explorer.