Google Maps just keeps getting better and better. Now in select cities in the US and the world, you can use Google Maps to get information on how to get from one place to another via public transportation. Just go to http://maps.google.com/transit and enter your starting and ending destination and the time you need to leave or arrive. It'll tell you exactly what buses/trains you need to take, what transfers you need to make, and how long your trip will take.

If you are taking public transportation, this is definitely the best way to plan your trip. It's way better than trying to read several maps/route maps at one time with all sorts of tiny type. Just enter your information into Google Transit and you are done.