jasond, solar cells are coming down cheaper, there still expensive but it's a investment that pays for it self. The one I upgrade to was a 40 watt cell. It is a tough cell, I can rough house it reasonably and is water proof in case of rain or shelter. If you are interested in setting on up, see some of my older posts on solar with a search of falcon5000 and select a year back of I would be glad to answer any questions if I can. I believe we should have the brain to know how to survive without anything, and equipment helps make everything a whole lot easier. The old saying work smarter not harder. I would definitely get a 20 watt or greater cell and if you look at this vendor's store (vitabon) he has great prices. If you google around you may find he's the cheapest.
http://cgi.ebay.com/40-Watt-Foldable-Sol...1QQcmdZViewItemThis is a 40 Watt Foldable Solar Panel. It is made of thin-film, lightweight solar technology. It is good for charging 12-16 volt batteries. Use for mobile electronic devices or charging lead-acid batteries on campers, trailers, RVs or farm equipment. Solar trickle charging has proven to extend battery life preventing batteries from deep discharge, saving money and time.
Also available, (sold seperately), is the solar cable kit that will enable connection to several devices. The cable kit comes with the following pieces; battery clamps, 8' extension cord, 2.5 mm plug (for portable battery packs), and a male and female cigarette lighter adapter.