A big piece of the iPhone's battery life issues are how you have apps set.

First, unless you need Bluetooth and GPS enabled, disable them. Disable WiFi when you get away from WiFi coverage.

Then disable "push" notifications for any apps where you don't need to have an update from the server ASAP. I'm running three email applications, and I have only one of them set to "push" and all others are set to poll the server either at 30 minute or 60 minute intervals.