Something I've learned from not having a cell phone but having a wifi device, if you walk long enough you'll find a free access point. In the Atlanta airport it's in concourse A, around gate 21.

This is where I've camped out, sort of. I found an outlet (my iPod was down to 20%), but it's not in a comfortable space. I'm on the floor in an otherwise empty terminal.

The janitorial staff is very pleasant.