Bill, from my understanding, the peloton is the main group of riders. Armstrong will typically finish with the main group on a sprinting stage as that's not his strength.
I couldn't agree more about the spectators though. I remember once in the Giro (tour of Italy) when the spectators were particularly bad, running along side the riders and getting in the way. Finally, Simoni punched a spectator out. He was kicked off the Giro that year, but has come back since and won it this year.
The motorcycles have caused some huge crashes. I can remember one last year in the Tour of Spain that took out a good portion of the riders, including USPS rider Mike Berry (I think that's the spelling he uses).