Save the environment - take local transit. Here are a few Google transit maps mashups.
Toronto google transit map
The Toronto Transit System google map has been mashed up here. Giving us a a nice birdseye view of the Toronto Transit system, complete with station street addresses.
Chicago google transit map
The windy city represents it Chicago transit system here. The Chicago google transit maps mashup has complete station locations with line colors, and a guide to let you know exaclty what restaurants, bars, and wifi locations are in the area.
New York google transit map
New York drop it down with its version of the New York City subway system. Featuring a nice point and click on your location and destination. The google map mashup will actually fill you in on detailed route. With complete walking distance estimator, and time required to get to your selected destination.
Seattles google maps mashup plots your closest bus stop locations by your chosen location. It will also give you route and traffic conditions.
The google maps mashup of San Francisco pin points San Fran routes, and stops along your route.
Boston google transit maps will let you select your location and destination, and plot a route by finding the nearest subway station to your location. Simply enter the address and click search.
In London, there is a google maps mashup of the entire London underground system. Plotting the routes for each different tube.