iZAP Lithium Battery for the iPod
ZAP is a company that specializes in battery powered cars and modifying Smart Cars to be legal in the states. They have turned their powerful battery knowledge toward the iPod with astounding results.
According to ZAP, their lithium batteries for the iPod will extend your listening time to 60 hours. You could go on a remote camping trip and never have to charge your iPod, even if you listened for the entire trip. You might even run out of music to listen to before you ran out of battery life.
The only glitch is the $50 price tag for the battery and the six hour charging time. If you find yourself separated from places to recharge your iPod quite often, then you might be interested in this battery.