Darren Jefford just posted about the Work Item Type Designer that he's been working on for a while. This designer was built using early versions of the DSL Toolkit, and now he's updating it to the Feb CTP. On the bright side, there was a lot of custom code that he no longer needed because many of those things have been rolled into the toolkit.
The Work Item Type Designer allows you to extend the VSTS work item system, by defining your own work item types and the state transitions that the work items may go through. Currently, this is only allowed in Team Foundation Server by writing a complex XML file by hand, but Darren's designer allows an admin to do this through a graphical designer. It's nice to have other parts of Team System starting to look at how they can use DSL Tools to expose some of their functionality.