When installing TFS in a single or dual server configuration you may have to modify your firewall to allow the Application Tier, Data Tier and Build Server to communicate. Here are the ports used by the different parts of TFS.
|SharePoint Central Administration||17012|
|Team Foundation Server||8080|
|TFS Build Remoting||9191|
|SQL Server Browser Service||1434|
|SQL Server Monitoring||1444|
|SQL Server Analysis Services Redirector||2382|
|SQL Server Reporting Services||80|
I haven’t reviewed TFS 2008 yet, but I would venture a guess that most, if not all, of these remain the same with possible additions.