If you've got an Android phone, pick up Juice Defender from the apps market. It's great. The thing intelligently turns services off when you're not using them. It just about doubles my phone's battery life. The phone is a bit groggy when waking up as it takes a while to restart the services, but once you get beyond that, the tool works without a hitch.
Here's the Juice Defender website. If you are reading this from your phone, you can probably install it from there.