I'm in love with these people. They use the pictures that you select from your gallery on flickr or bebo or fotolog or vox or livejournal or views from your second life or habbo. Then they print 'em on the front of these cute little 28 x 70 mm cards. Then you tell them some text to put on the back of the card, mostly just something static but they also allow you to include basic variables like "the name of the picture" and stuff.
Twenty bucks gets you one hundred cards. I threw together a few pictures of the cat, some flowers, and a derby dolls bout for the front of the cards; then I threw some pithy text and the URL for my podcast on the back. I handed 'em out at work to everyone who came by my desk and people loved them. In fact, I had none left after *one* day.
I think I love it because it's just a nice, simple, versatile thing. You could make some really fun calling cards with this app ... or you could make a *killer* meme initialization vector. The cards make you crop your images so narrow that the viewer naturally wants to see what the rest of the photo looked like ... so you put a URL or text on the back that lets them see the rest of "the big picture" and it's irresistible!