A couple in Poland were spotted riding a bike side-by-side down the street. This kind of bicycle is called the Sociable; get a look at the front end of one at Wikipedia. It seems quite a bit more sociable than a standard tandem bike, in which you are either staring at the butt in front of you or wondering whether the person behind you is pulling his weight. -via Daily Picks and Flicks
I like the older bike at the Wikipedia page because both riders can steer. I had a tandem bike, and the most unnerving part of taking the back seat was the lack of control.