These are lots of links to do with bikes, both RDs and other bikes.

ePowerSports . American based site selling biking goods at good rates, classifieds and community section.

PGM Motorcyles Spares - specialising in new and used RD parts.

RD dragracing from Team RNR 

Doug Johnson's Motocarrera site and home of ACTSO

The Jade Racing site, home of the Worlds Quickest RD400

The SuperTwins site. Info on The National Association of Supertwins drag racing club

Michael Moore'sEuro Spares site.