I built one of these:
http://www.instructables.com/id/How-to-make-a-solar-iPodiPhone-charger-aka-MightI substituted the solar panel in the instructions with this one:
http://greenenergiesllc.com/zencart/index.php?main_page=product_info&cPath=3&products_id=13It seems to work very well, though you can probably buy something similar for less than what I spent making it. It was a fun project though.