Efficient use of Public Transportation

I recently read an interesting post on Dumb little man, about two amazing websites Google Transit and Hopstop. These websites provide an efficent way to plan your intracity travel using the public transport systems in couple of major US cities. One needs to enter in the starting and destination address and the time of travelling and these websites will pull the most efficient way to reach ones destination with details about the subway and/or bus system to be used along with the distance and timing details throughout the trip. It is like taking Yahoo maps or Google maps with out your personal vehicle and replacing with the respective public transport system.
Hopstop caters to major North eastern cities like New York, Boston , Chicago etc, while Google transit has been focusing more on California cites and random cities throughout the country. However Google transit is expanding to other cities.
So next time when you make a trip to one of the big cities try using these websites to plan your public transport system, giving you more time to enjoy the city.