The folks over at Make are so smart sometimes it hurts. This is just another one of those times as this repurposed pop tab idea is sheer brilliance. I've had many custom art pieces that aren't mounted in a traditional frame and hanging them can be quite a chore. Those little alligator teeth never really hold up and you're rather limited with easily accessible hardware you can use to hang it.
Using a pop tab from a used soda can would be ideal (and inexpensive!), just as long as you remove it with the ring in tact. Hop over to Make for a tutorial on removing the tab perfectly each time and read more on this great how to project!