Have you installed any apps to monitor battery drain? I use GSAM Battery Monitor and every time I start to see weird things with my battery, I have a look to see which app is running wild. Removing the app usually sets my phone back to very good battery life. The other day HD Widgets updated their app and all of a sudden I was dropping battery life about 15% per hour when hardly using the phone. HD was the culprit, removing it put me back to normal again. This happens often when companies update their apps.
One other thing, does you phone run hot? In the notification screen, you can see the current temp of your phone. If your battery is draining fast, it will run hot.