(I saw this sign in NYC last fall. Clever marketing! N.P.)
Your starting point (intersection, specific venue or address) will show as a red dot and you'll see all the options marked with a (what else?) green P, with a list on the left hand menu where the options can be sorted by distance or by price.
Click on any green P on the resulting map and a window will pop up with more information such as the number of spaces, height restrictions and a photo of the parking lot so you can recognize it at sight when you get there. Click a link in the window and you will get even more info like the accepted modes of payment and the maximum daily rate.
They even have an app for that! (Updated Nov. 17, 2012)