I wrote a program that automatically updates a KML file with the locations of all of the local busses in Boulder, CO. The tracking data comes from a server run by Intuicom, a local company that installed the GPS trackers in the busses. The data comes in a slightly modified NMEA format, but it's not too difficult to decode. My program was written in C#, and kind of kludged together with code from several past projects of mine, but it seems to work great.
I'll leave it running on my home server for a while so everyone can get a look. If people really want it and my boss gives the OK, maybe I'll post the executable or source code.