According to Brian Harry, one of the real novelties in TFS 2010 will be the concept called Team Project Collections.

“In TFS 2010 a TFS farm hosts Team Project Collections and not just Team Projects as it was in TFS 2008. A Team Project Collection is a group of related Team Projects and a TFS farm can host many Team Project Collections. To try to make an analogy with TFS 2008, it’s as if TFS 2008 could host exactly 1 Team Project Collection per physical TFS server. Just about any statement you might make about a TFS 2008 server would apply to a TFS 2010 Team Project Collection (TPC)”.

Moreover, Team Project Collections are independent of each other. That means that two TPCs can both have a work items with the same work item ID. In TFS 2008 things could be identified by server URL + ID. In TFS 2010 one can identify them by server URL + team project collection + ID.

Here is the illustration:

This is what one sees when connecting to a TFS server in TFS 2008. There is a possibility to choose a server and one or several Team Projects out of the list to work on.

In TFS 2010, the Connect to TFS dialog looks like this:

There is now a list of Team Project Collections (currently labeled “Directory”)on the left, and on the right, there is a list of Team Projects within the selected Collection. The client will only allow you to connect to projects in one TPC at a time.