Team Project Collections are a great new feature in TFS 2010, that allow you to organize all your team projects into groups.
Here is what you need to do to create a new team project collection (TPC)
1. Log in to your TFS server.
2. Bring up your TFS Administration Console
3. Click on “Team Projection Collections” under the “Application Tier” node
4. Click on “Create Collection” and go through the wizard of setting up the TPC. (I have never had to modify the default settings while going through this process).
5. Important: Users that will be in-charge of creating team projects within the TPC, need to be added to the “Site Collection Administrators” list. (instructions can be found at the following post: TFS – Unable to create a team project due to Sharepoint permissions)