Get an iPhone battery pack for $6.99 shipped
For about the price of a pair of lithium AA batteries, you can nab this travel-friendly battery pack--which just so happens to come with a pair of lithium AA batteries.
Need extra power for your iPhone or iPod Touch? Hey, who doesn't? Buy.com has the Energizer Energi To Go Battery Charger for $6.99 shipped. I'm going to make this quick, because I guarantee these will sell out.
The Energi To Go can power and recharge any dockable iPod, including 1st-generation and 3G iPhones, Touches, Nanos, and Minis. It relies on a pair of AA batteries, preferably of the lithium ion variety (two of which are included!). You can use regular alkaline batteries in a pinch, but you won't get the same amount of run time.
Even if you spring for a set of rechargeable AA's (not a bad idea), your overall cost will be well below that of traditional power packs. Witness theby Dong Ngo: At $60, it's nearly nine times more expensive than the Energi To Go.
Indeed, this is the best deal I've seen yet on a portable power supply, so grab one before they're gone. (Seriously, my inner cheapskate says these won't last the day.) If you miss out, Meritline still has the nearly-as-good.