When I needed portable power for my Small Form Factor WiMax project, I remembered seeing mention of Sundance Solar over at TreeHugger. Their $369 solar kit looked like just what I needed. The kit is pretty simple: a solar cell (24W cell pictured above) and a rechargeable power pack made by Xantrex. You can use the included power adapter to top off the power pack before you go out in the field, and the solar cell will charge up the pack while you work (although the manual says you shouldn’t use the power pack while it’s charging from the AC adapter, I couldn’t find such a warning for solar charging).