Bus Monster provides live, real-time tracking of Seattle Metro bus locations, bus stop locating, route planning and even alarms for when your bus is about to arrive at your stop, all using the Google Maps interface. Plot your routes, get schedules, and see satelite photos of your bus stops.

It combines Google Maps, the King County Metro Trip Planner, and the UW Intelligent Transportation Systems project, all of which provided this functionality separately using separate interfaces. The combination is just plain slick. Built by a coworker of mine, kudos to him.