As a part of greening up the earth, Google Transit will tell you the quickest way to get from Point A to B using mass transit in the city.
We tried it out, starting out at 4 Times Square and ending at 770 Broadway; one might think taking the N/Q/R/W would be the quickest route -- but that person would be wrong. Apparently the best way to do this is by using your own two feet; Google says walk it! Not a bad idea, but perhaps this option is showing up because, despite Google having major office space in NYC, they haven't fully translated our transit system yet.
New Yorkers can map how they're helping out the earth today, however, right here. So far locals have been encouraging others to "use mugs instead of plastic cups," and one is organizing "a week long festival of Earth friendly activities at SUNY Potsdam."