If you commute to work in your car or on your bike then you really need a battery backup and charger for your USB devices like your cell phone and MP3 player. Use the commute time to keep your backup battery fully charged.
The one I bought is the Scosche solBat II for about $25.00. It's a solar powered backup battery and charger for most USB devices. It is a very simple device consisting of pack about the size of a small cell phone. To charge it initially you use the supplied USB cable and plug it into your computer or into a USB wall outlet adapter and charge it for 4 or 5 hours. Alternatively you can just stick it in the sun for 4-5 days (!), maybe longer in Seattle, to fully charge. I went with the "stick it in my computer over night" route. It also comes with a cradle and suction cups so you can stick it to your windshield to keep it charged after the initial charge.
Forgot to recharge your cell phone or MP3 player last night? No worries, use your solBat. To use it, all you do is take the USB cable that came with your phone or other device and plug it into the USB port in the solBat and you're good to go. What I really like about the solBat is the lack of adapter tips! Every other battery/charger I looked at had a special cable that had interchangeable tips depending on what device you wanted to charge. If they don't have a tip for your device you're out of luck. Some can sell you tips for the less popular devices; like I want to spend even more money! I used to have a real hard time finding tips for my Samsung phone. For you outdoor types there is also a carabiner to clip onto your belt, bike or backpack.