For the past couple of years, a british company Better Energy Systems has offered a nifty and environmentally responsible tool called Solio tagged as a 'portable solar charger'. Its battery can be charged using solar power (full charge takes 8 to 10 hours of direct sun) or the old fahioned way using an adapter plugged in your usual electric outlet (in about 5 hours).
It works with MP3 players, Cell Phones and PDA's.

It costs around $100.00 and can be bought through JR World, Best Buy, Apple to name a few.
The design team at Coudal reminded us of its existence.