The Ann Arbor plow truck public tracking page shows where the snow plows are out and about in Ann Arbor.
This view shows 4 of the 5 trucks that were out on Monday evening, January 2, 2012.
Plow routes are color coded, and plow trucks are numbered. One tip: if you are using Chrome, turn on and off the "label" field to get the trucks to show.
The system is build by Radio Satellite Integrators, and uses ESRI map technology. I don't have an explanation for the US-12 shield on Jackson Road.