Some Chinese manufacturer recently came up with a quick battery replacement solution for the iPhone. Their battery replacement kit costs a lousy $20, so instead of sending off your iPhone to Apple you may be interested in a way to change your dead battery faster. The package includes a 1400mAh, 3.7V iPhone battery, something like a screwdriver, a plastic chiv, and instructions (in what language remains a question). Just crack open your handset and replace the battery.
One thing concerns me though. You can't get a qualitative product for such a low price, so if you decided to try it, you're on your own...