Google added a new feature to its extremely useful Maps service. When searching Google Maps there's new option called transit under "More", click transit, the map will display an overlay of each of the available modes of transportation (note that while trains and subways will appear while zoomed out, you’ll need to zoom further in to see more regional buses and trolleys).
This feature is currently available for over 50 cities around the world such as London, Berlin, Paris, Chicago, Seattle, etc. but New York is excluded. More on the story and some screen shots