I downloaded advanced task killer froyo from the market. It gives you a list of what's running in the background and you can kill whatever programs you don't want to use. Also adjust your screen brightness and screen shut off time. I work 8 hours, 9 total of being without on charge and still have about 50% battery life left. This is using internet, games and playing music for about 3 hours
I agree. Screen brightness is key to battery consumption. Also, signal strength, the phone draws more power to connect to the wireless network in low signal areas.
I use Watchdog. It gives me a breakdown of running apps and CPU usage. There may be several apps that are "running", but they do not consume system resources. They are just waiting in the background. When you call up the app, it should run quickly.
I usually keep screen brightness at 15-25% which is sufficient for indoor use. After about 7hrs, my battery bar turns yellow, and I swap out the battery. Batteries are about $30 on Amazon.