Do you have a exchange account configured?
It's known to drain your battery at that rate when not set to "Push" (generic Wake Lock problem in Froyo)
Also, if you don't mind spending a few bucks, install System Panel app and let it monitor CPU, that way you'll find out which apps are the top battery users (while asleep, battery drain is fairly equal to cpu usage, so the top cpu-usings apps will be the drainers). I have 75% battery left after 10 hours of light usage with Bluetooth. Auto Rotation and 3G enabled.