This method is a little high-tech, but there's an easy low-tech modification for it.
Step 1: Get a Cheap Frame
My favorite find is the ISIG frame. Two frames that hold 5x7 photos for $3! A tasty deal and even my cat dug the smell when I tore the wrapper off.
Step 2: Take Everything Out
Step 3: Etch the Addresses
So you don't have a laser cutter? I hear ya. Just grab a Sharpie and draw them on yourself. There doesn't need to be anything high-tech with this.
Step 4: Glue it In
Step 5: Mail it Off
I mailed two of these cards in the bay area of Northern California. One went about two miles and the other went about 30 on its way to Stanford. Strangely enough, the Stanford card cracked in almost the exact same way as the stencil postcard I mailed to Brooklyn. Weird.
Yesterday, I mailed off two more to Brooklyn. Don't know if they'll survive the trip.