Thank you Henry :D
Have you sent any through the mail yet? There are some guidelines that the Post Office requires....must be "under" 1/4" thick...must be 4" x 6" and must have the words "POST CARD" on the back where your writing is. Then you can place one of the self-stick post card stamps on it above the address and place them in the mail! Be sure you secure the edges of your fabric so the fabric doesn't peel.
You will soon be looking for "subject matter" to put on your cards! Little miniature patterns (paper pieced) work really well. Each card then becomes its own little personal quilt.