My first "hack" as a teenager was soldering a USB cable into the place the USB mini port was on a palm I was using as an ereader. The port would just become detached from the board if you looked at it funny; so this worked pretty well. I could just plug the whole device in to charge from then on.

Then I realized that the three volts that were supplied from a pair of AA batteries was really more of a suggestion. That summer, lots of gadgets I had became "USB powered"