I use the Sunlinq folding panel. It's rubberized and flexible, even the panels can be flexed somewhat, unlike the goalzero which has rigid panels and thick nylon covering. According to the Sunlinq website, the panel weighs 4oz. I have not weighed it yet, but it sounds close. I've also trimmed off a great deal of the excess rubber, which provides no functionality, and should save another oz or so.
I've had good luck with the panel. It charges iPhone, iPad, nook color, Tikka core headlamp, and my Streamlight rechargeable flashlight, all in about the same amount of time as plugging them into the wall in full sun.
I had previously tried the Brunton folding panel that REI sells, and it would not charge the iPhone or nook.