Originally Posted by 3Lph
I'm still waiting for tandem mountain biking, tandem slalom bmx, tandem downhill racing, that sort of thing.
Tandem MTB and tandem downhill is done. But since there are so few they usually don't have anyone to race against. There are many rigid MTB style tandems and a few FS models available (e.g. Ellsworth Witness, Ventana El Conquistador de Montaņas,...)
http://www.flickr.com/photos/anderson/44008731/