I have no idea why these are called "moo" cards, but they are similar to business cards only about half the size - approximately 1" x 2 3/4". They are available through Flickr and come in sets of 100. They are made from any combination of photos you have stored on Flickr and can have up to 6 lines of text on the back.
I ordered mine a few weeks ago with ten copies of my collages and they came in Friday's mail. It is so fun to see your own art and name on cards! And the artwork looks so different in miniature! I am loving these - makes me feel almost "professional!" I am hoping to give them to my fellow store employees as well as our customers so we can keep in touch after Recollections closes.