I found one at Staples that can charge two devices at once, and it works. I've never found one that can charge four devices, but you could just buy two of them. It was on sale for $10 and looked like a normal USB charger that plugs in except that it has two ports.

I'd like to get something like this to reduce clutter, but in looking on Amazon, I've seen many complaints that the devices are too low-powered to actually charge multiple devices simultaneously (especially if one is an iPad). Has anyone found one that can actually charge two iPads, a Kindle, and an iPhone simultaneously? (Okay, maybe I should have put this in the "First World problems" thread.) Thanks.