DX Dual USB Solar Powered Battery Charger 232365
This is a rather cheap, but handy little battery pack I picked up from Deal Extreme. The capacity is stated as around 8,000mAh, which seems about right - I've had a good two to three charges of an iPhone 5 from this device.
The built-in solar panel is around 1.5 watts (300mA @ 5v) so it's going to take 27 hours of full sunshine to fully charge the built-in battery. With the best will in the world it's going to take around 4 days to charge this from flat to full, so you should think of the built-in panel as a way to ensure the battery stays topped up when not in use rather than anything else!
The supplied cable has three different outputs, meaning it's a good little compact cable you can probably cover all bases with - works for charging the device as well as charging other items.
I haven't managed to measure more than 600 mA from the "1 Amp" port and the most I've seen from the "2 amp" port is around 900mA, even allowing for the inaccuracies of my USB power tester I'd say it's a little under-spec, but still, plenty to give an iPhone or iPad a jolt of charge.