Typically sommewhat organized, but not marked or anything. Several stops, which may or may not have an order. Often these are announced at the starting line so the racers have to think fast to find the best routes. Several of them have prizes (mess bags, etc). Some are annual, others just kind of happen...

I've yet to compete in one. There were several this summer out here, but I was riding my track bike and not quite foolish or brave enough to want to race with no brakes. My first one will be the Stuperbowl in February. I was talking to one of this year's organizers, and it sounds like it's going to be a lot of fun. Unfortunatly, not all of the stops will be bars this year, so if I want to try for the 'first to drink at every stop' prize, I'll have to carry some extra weight. Supposedly package delivery will be involved as well...