Dan Kershaw has produced (and updated) a whitepaper for folks who don't want their TFS AppTier and SharePoint servers on the same machine.
Unfortunately, the doc seems to have moved since most of the links out there were created. As of right now, it's located here: http://msdn2.microsoft.com/en-us/teamsystem/aa718901.aspx
Warning: I'll quote Brian's post on the original link - this process is NOT simple: "The instructions are neither simple nor short. I really don't recommend doing it unless you are ready to pull your hair out for a day or two getting all of the configuration pieces in place. The simplest way to think of it is that TFS V1 does not support it but future versions will. However, some of you are brave souls, undaunted by challenging problems. For you fearless few, this article should provide you the information you need to configure TFS and SharePoint.
Good luck :)"
I'll also repeat Brian's comment that we'll have a better mechanism for this in a future release - the whitepaper is for those who just can't wait.
This is the time, this is the place...