Using the Microsoft.TeamFoundation.WorkItemTracking.Controls assembly it is possibe to display WorkItems. Here is a little demo application that will display all the WorkItems that have been changed by one of the given users in the given range

screenshot of workitemtracker application

Feel free to download the source:

Edit (05/03/2008):

Refactored the code a little and added some features like sortable columns, loading default tfsserver and users from App.Config, …