I can turn sync on/off in the Power Control bar. Which applications actually use this sync setting? Is that only Google-based products (calendar, contacts, gmail) or does it also influence apps like IMAP email, Evernote, etc?
I think you mean the Auto-sync. Go to "Settings -> Accounts & sync". You will find which apps are using the sync function under Manage accounts. Only the apps in the list will be influenced.
To identify the app that is causing sync. Go to "Settings -> Applications -> Manage applications-> click "Uninstall update" for the app (This is due to the updates that added background sync. only few app show this). These apps are the culprits to drain your battery.