At the moment I like the JOOS Orange solar charger,
http://solarjoos.com/products. I'm still testing it out so can't say anything definitive, but in day to day charging it works as promised. I bought it for a last ditch charger of cell phones and other USB devices, in the event I'm away from my car (primary charger) and the power is absolutely out. The JOOS is sturdy, waterproof, and holds a great amount of charging power. I like that I can set it out in the sun and then charge two cell phones with ease, or a kindle etc if that's what I had. I bought an earlier flexible solar cell and its difficult to fully recharge one phone from that thing.
98% of the time I would recharge from my car, especially if I am out and about, that's easier. But the JOOS has held up well for a month or two and performed as promised.