Smike AG in Lucerne, Switzerland.
The side-car can easily be attached with just a few turns to take a second person along or carry loads. An optional electric motor makes the trip even easier for the cyclist, and an optional child seat for the sidecar allows the cyclist to carry an infant on the bike. The 165 pound weight limit for the sidecar limits passengers to children and smaller adults.
The 1 meter wide Smike is road legal in Switzerland and Germany, although local regulations in Switzerland may limit its use. In the United States, there are no width restrictions on pedalcycles.
Although Smike claims to be the first builder of bicycle sidecars, they actually have a long history in the UK. There's an interesting discussion on bicycle sidecars and handling over at the helmet nazi site.
Seen at German language Rad Spannerei blog. And who can forget Jezz's bicycle sidecar at 63x.com?