Moo cards are like business cards only smaller. Moo card dimensions are 28mm by 70mm, which is very roughly 1" x 2 3/4" just to give some idea.
Cards are purchased 100 at a time and you can use up to 100 different images. Info is on the back, so you get full use of the front of the card. They are fun and new enough so that people take notice when you share them. Moo cards may be purchased from MOO.com.
Here are my past and present cards: