I don't have one of these Joos portable solar power chargers, but they look good, and the specs are impressive. The manufacturer claims that it charges at least 3 1/2 times faster than other portable solar chargers at the same price ($139.95, but they are on sale for $99). They also claim that one hour in the direct sun equals two hours of 3G talk time, and that the battery pack has enough energy to charge a smart phone "at least four times over." It's waterproof, too.
It also comes with a utility for windows and OS X that shows you how charged your battery is, how much instantaneous solar power is being generated, and the total amount of energy your charger has produced. Unfortunately it looks like the charger is sold out, but you can go to the website and enter your e-mail address so that when more units are available you can buy it for the sale price of $99.
If you have experience with this charger, I would appreciate it if you could review it in the comments section of this post.
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. His new book is Maker Dad: Lunch Box Guitars, Antigravity Jars, and 22 Other Incredibly Cool Father-Daughter DIY Projects