Arron Hallberg has a really interesting post on his blog on how to add a custom task to the Team Foundation Build Process. The possibilities of this type of extensibility which most areas of TFS have out of the box are truly amazing.
I have worked with a few code generation tools in the past, Wilson ORMapper, LLBLGen Pro, and now CodeSmith and immediately I thought how great it would be to automate these code generation tools into the build process. Ill probably take a stab at this very soon.