- Set my phone to always keep wi-fi on during sleep (under Wi-Fi, under Advanced in the menu). I have weak cellular coverage in my house, so falling back to cellular isn't necessarily better for battery.
- Disable Currents from syncing. It is a heavy abuser, and I don't use it.
Problem solved.
By the way, two apps I have used for keeping an eye on battery are BetterBatteryStats (good for investigation) and Battery Widget? Reborn! Pro (general purpose, good for keeping an eye on drain).