As I mention in the text for another project most business cards are boring. I'm always on the lookout for ways to make my business card, which is basically my representation in information space, stand out from those of the crowd.
Most people have business cards that are single sided, but the card actually has two sides, it's just that only one of them is printed upon. These business cards only have one side. If you put your finger on them and trace it around, you'll wind up right back where you started. Even though I had to take two pictures to show the whole card, and the card is flattened out so it will fit in my wallet, the card only has one side, officially. Look up "Moebius Strip" in the encyclopedia and you'll find out.
The real trick to this project wasn't figuring out how to print onto paper in a way that I could make a moebius strip out of the results, but figuring out how to print onto paper so that the resulting moebius strip would be the same size as a standard business card once it was flattened. I'm no math genius, so the geometry was a hit or miss proposition. I have a stack of five prototypes that get incrementally closer to the final product.
These are kind of a pain to make, so I really haven't gotten around to using them as actual business cards. I need to update the design for my new email address and URL, though. I also should figure out something keener for the third panel of each view than the boring rainbow gradients I have there now.