The Airnergy Charger is amazing.
This little box has, inside it, some kind of circuitry that harvests WiFi energy out of the air and converts it into electricity. This has been done before, but the Airnergy is able to harvest electricity with a high enough efficiency to make it practically useful: on the CES floor, they were able to charge a BlackBerry from 30% to full in about 90 minutes, using nothing but ambient WiFi signals as a power source.
The Airnergy has a battery inside it, so you can just carry it around and as long as you’re near some WiFi, it charges itself. Unlike a solar charger, it works at night and you can keep it in your pocket. Of course, proximity to the WiFi source and the number of WiFi sources is important, but at the rate it charges, if you have a home wireless network you could probably just leave anywhere in your house overnight and it would be pretty close to full in the morning.