You can get a USB adapter that plugs into your cigarette lighter in your car. They can be extremely useful. I just got one the other day and I love it. Use it to power or charge your MP3 player, GPS unit, camera, etc. My BlackBerry uses a standard USB cable so I charge my cell phone battery. Don’t buy the proprietary $30 chargers for EACH device. If your electronics have power options via USB, just power it with the cigarette lighter USB converter.
Wal-Mart, OfficeMax, and Radio Shack probably all have them. I found several suppliers online for less than $5. Here are some links if you prefer to shop from home:
http://tinyurl.com/5bx38h (has light to indicate power, 2 USB ports)
http://tinyurl.com/636mat (great photos and reviews, no light and only single port)
(There are also some that convert a 110 home power outlet to a USB charger. That’d be great for traveling / hotels.)