A thread is active in the Eris forum that equally would apply to the Hero (Eris and Hero are basically the same phone). Some apps are resource hogs and knowing about them gives you the knowledge to improve battery life.
http://androidforums.com/htc-droid-eris/40395-known-resource-hog-apps.html
http://androidforums.com/htc-droid-eris/40395-known-resource-hog-apps.html