One of our new "killer" features coming in our TFS 2010 (Rosario) release is what we call "Gated Checkin".  It is a feature that enables you validate checkins on a separate build machine before the checkin happens.  I think of it as an evolution of continuous integration that scales a little better for large teams.  Continuous integration finds integration issues quickly be constantly building checkins and notifying you of breaks.  The downside is that the "current" code is broken until someone fixes it.  Gated checkin does the same thing but before the check in and prevents the current code from getting broken.

If you pick up our CTP that's coming this fall, you can try out the gated checkin feature.

If you really like it and are interested in doing something similar with TFS 2008 (before TFS 2010) comes out, you can check out this new project on CodePlex: http://www.codeplex.com/BuddyBuild.  It is a similar kind of system developed by an internal team here at Microsoft.  It is not a part of TFS and the implementation is unrelated to the TFS 2010 Gated checkin feature.  However, I've heard a few good things about it and you may find it valuable if you are looking for the next step past continuous integration.

Brian