A before & after from MirrEdge
Apartment Therapy took a look at MirrEdge, a system for framing those raw edges. AT was skeptical, though, saying that the selection left something to be desired. I have to agree. And also, this is suuuch an easy DIY!
You've got a lot of options for getting your mirror into frame, so to speak. All of it requires very careful measuring, though, so whip out that ol' tape measure, measure all the dimensions of the mirror, and write it down in your neatest handwriting. Once you know what size you're dealing with, you can purchase an art/picture frame, and mount it to the mirror. You could use glue, caulking, or if you're renting, removable adhesive strips like 3M's "command" line. You can use the same mounting techniques on all sorts of different materials. Have crown molding cut to fit your mirror. Use pieces of driftwood or fallen branches for a woodsy look. Or stick up photographs, playing cards, or even paint chips from your last makeover project. Covering those sharp glass edges will give your vanity a finished and more personalized look.
After all, like any other part of your home, you want your vanity mirror to reflect who you are. Uh, okay, I know that mirrors reflect already. But you know what I mean.