A couple of years ago we posted about the "Minty" version of an Altoids tin solar charger. Here's another version of the Altoids tin type of usb solar charger that comes in under $30.00 for DIY'ers. You don't have to use an Altoids tin for this version.
This little version is from Joshua Zimmerman and requires several simple tools and parts. His version of the usb solar charger is under is under $30 and he also has a site that has ready-made versions and all types of DIY solar project kits and parts. Something to do on a hot sunny day during the upcoming summer months.
Instructions for DIY solar usb charger at Instructables.
Solar DIY kits and parts at Brown Dog Gadgets.