The easiest way is to create a new solution file. Nothing prevents you from having multiple solutions that reference the same projects (or some subset).
Another way is to create a new configuration. In Solution Explorer, right-click the root node β Configuration Manager. In addition to standard configurations such as "debug" or "release", you can create your own. For each config + platform combination, you can use the checkboxes below to determine which projects will be created and which parameters they will use.
No matter what you choose, you will edit the TFSBuild.proj file to indicate the desired solution and / or configuration. MSDN instructions: http://msdn.microsoft.com/en-us/library/bb399127.aspx