A recent run of powertop discovered that the webcam in my Acer Extensa 5620Z was causing a significant amount of wakeups. I never use it, in fact its covered up with a sticker.
[ 6.888500] usb 1-1: Product: Acer CrystalEye webcam[ 15.287631] uvcvideo: Found UVC 1.00 device Acer CrystalEye webcam (064e:a101)[ 15.288506] input: Acer CrystalEye webcam as /class/input/input6
zzillezz.net turned a similar webcam off with "blacklist gspca". I'm using "blacklist uvcvideo".
While I was at it, I also blacklisted a few other modules to save RAM as my laptop recently lost 2GB of RAM. :-(