I think one of the best mobile power sources is the apc mobile power pack.. This will charge anything that has a usb connection.. I can keep my Garmin 305, Ipod and Samsung phone all charged up when on the road.. You sometimes have to buy a charging usb cable for your phone but most phones have this option and the power pack lasts a long time.. These can be found on ebay for around 50.00-60.00..

here is more info: http://www.apc.com/resource/include/...B10&tab=models