Bus Monster is an inspiring example of web services integration.

Bus Monster begins with Google Maps, overlays bus stops by scraping the King County Metro - Trip Planner, adds real-time estimates of bus arrival times using the REST interface to the UW Intelligent Transit Systems, and adds traffic images using a number of Washington state web sites (to convince you to take the bus!)

The work required to glue together services isn’t always pretty, but the results can be stunning.