Finding out about AP rates?

[button409]

I'm going to wdw in Jan, and am going to buy an AP when I get there, as planning 2 trips to wdw in 2008! Whats the deal with AP rates? I know you dont have to have the AP to book the rate, but how will I find out about the rates - until I have the AP I can't log on to the AP website? Are they limited to a certain number of rooms?
Also does anyone know the AP benefits for 2008? Thanks!