My aging Motorola phone finally gave it up when its battery died. Not quite ready for a brand new phone (still waiting for the Sony Bluetooth phone on the Sprint network), I planned to just buy a new battery. Sticker shock ensued when I saw that Sprint charges $60 for a replacement -- that's before tax & shipping.
A quick web search later brought me to PhoneBatteries.com. The same exact battery (made by Motorola) was only $27. Even considering $10 for 2nd-day delivery, this is a bargain. They're hooked in through Yahoo Stores and I'd highly recommend these guys if you ever need a new battery.