If you have time, I suggest you close all apps, restart the phone, disable all radios and leave it in airplane mode, and see if it still drains.
Did you update any apps lately? Do you have apps that push information to your phone home display, like a sports tracking app, or even Facebook? I turn all the “push” and “badges” notifications off on most of my apps on my iPod Touch because they tend to drain the battery. Skype is the worst - the automatic sign-on and constant refreshing just kills my iPod.
I’d go through the Settings for all your apps and see if there’s anything there that might suddenly be contributing to your phone constantly trying to connect to a service to get information.