I've tried to standardize many of my small electronics to use USB charging.

For example, my cell phone, and iPod Touch (PDA basically) and GPS can all be charged via USB.

In addition, I found a USB charger that can charge my cell phone battery externally:

http://www.amazon.com/gp/product/B002MVQFMW

Then, I keep one of these lithium ion powered rechargeable battery packs in my bag:

http://www.tekkeon.com/products-tekcharge1800.html

And lastly, I keep a small USB power brick and auto USB power adapter in my bag.

This combination of standardization and set of options provides a fair amount of flexibility.

I can charge my phone from the lithium ion power pack on the go, I can use it to charge a cell battery externally while I'm using the phone.

I can do all these from a car or wall plug if available. The lithium ion pack even uses USB for charging so I can charge it from my wall or auto plugs.

Adding a portable solar panel with auto or USB output would further enhance this configuration.

All in all, a little planning can go a long way.

FWIW, I also found it is very helpful to be able to charge two devices at a time instead of just one. It is a worthwhile exercise IMO to try to go a couple of days with only the charging options you have with you.

-john


http://www.sendstation.com/us/products/pocketdock/lineout-miniusb.html
http://www.usbfever.com/index_eproduct_view.php?products_id=41
http://www.tekkeon.com/products-tekcharge1550.html
http://www.tekkeon.com/productcart/pc/viewPrd.asp?idcategory=11&idproduct=121
http://www.amazon.com/Brunton-Solaris-12-Solar-charger/dp/B0019OOTNK
http://www.amazon.com/Powerjolt-Dual-Universal-USB-Charger/dp/B001Q2FM5E
http://www.amazon.com/DLO-002-9981-PowerBug-Wall-Charger/dp/B000NOPA9E