I've been looking at solar chargers for a while. Most of them are overpriced and underpowered. There is one coming out in a few months, Q3 2010, which is getting really good reviews for their pre-production reviews. It's called the SolarJoos. It will cost around $100, but it can charge an iPhone four times with it's internal battery. The best thing is that it is rugged and waterproof!
http://gizmodo.com/5584810/joos-oran...+%28Gizmodo%29