USB Fever's 3000mAh add-on promises 8.5 hours of talk time or 20 hours of delicious video playback for iPhones.
According to the manufacturer "it's not bulky either as it just extends a little at the bottom" — yeah right, and Steve Ballmer is just a little intense. The Super Charger is positively ginormous, but if you have a sherpa (or intern) to help you schlep it around, the battery pack can be picked up for $US60. It won't void any warranties, but it should. [USB Fever via Crunch Gear]