Check out the Sliding Task Lists project
If you're searching for a good MS AJAX tutorial, then check this nice demo application written by Ivan on his Coding Atlas blog (nice one, subscribed).
The good news is that he talks extensively about the project in a 5 parts tutorial and the application is hosted live here.
P.S. Ivan says that he's continuing to work on the project and thus he's going to add more parts to the tutorial... one more reason to subscribe to his blog :)