Randonneuring: Randonneuring is long-distance unsupported endurance cycling. This style of riding is non-competitive in nature, and self-sufficiency is paramount. When riders participate in randonneuring events, they are part of a long tradition that goes back to the beginning of the sport of cycling in France and Italy. Friendly camaraderie, not competition, is the hallmark of randonneuring.
-From RUSA website
The next PBP is in 2011.