This is a small console application that pulls user check in history out of a TFS instance. Admittedly check in count is not a very good metric of a user's contribution to a codebase - some developers prefer frequent small commits, while others prefer less frequent but more complete commits. Still, it's interesting information to look at.
Make sure to fill out the TFS server address and a list of pipe-delimited Active Directory domains to whitelist in the App.Config file, and run the utility.