I came up with this idea when a friend's sunglasses where broken, but the did have nice arms. so I screwed them on an other pair of glasses and created this nice look. its really easy you actually don't need an instructable for it.
also on my blog
Step 1: Materials
-2 pairs of sunglasses
-small screw driver
note: make shore that the sunglasses have the same attaching system so the arms can be switched.
Step 2: Screw
use the screw diver to remove the legs of the one sunglasses and attach them to the others. and your finished.