In no particular order

  Traditional Cowboys Sites that specialize in the art of the cowboy
15-12-28 Great Florida Cattle Drive Histrical reenactment you can join
  04-25-11 The Californios Ranch Roping contest
  10-08-06 Vaquero Enterprises Dedicated to the history of the California Vaquero
 
  Museums
  10-08-06 National Cowboy and Western Heritage Museum (Oklahoma City, OK)
  10-08-06 Pro Rodeo Hall of Fame and museum (Colorado Springs, CO)
  10-08-06 Oakdale Cowboy Museum Nice site but limited resource (Oakdale, CA)
  10-08-06 Brithsh Columbia Cowboy Museum Ranching and Rodeo (Williams Lake BC, Canada)
  10-08-06 Booth Art Museum Western Art (Cartersville, GA)
  10-08-06 Hubbard Museum of the Ameraicn West (Ruidoso Downs NM)
  10-08-06 Texas Cowboy Hall of Fame (Fort Worth TX)
  10-08-06 Cattle Raisers Museum limited online resources (Fort Worth TX)
  10-08-06 Desert Caballeros Western Museum (Wikensburg AZ)
  10-08-06 Autry National Center American Indian (Las Angeles, CA)
 
  The Horse Whispers Natural Horsemanship
  10-08-06 Monty Roberts One of the great horse communicators
  02-05-07 Mark Rashid I don't know how good he is but his site looks great
 
  Cowboy singers and poets
I have chosen for this section, entertainers who have actually been cowboys at sometime during their lives
  10-08-06 R.W. Hampton Singer
  10-08-06 Don Edwards Singer
  10-08-06 Red Steagall Singer, poet
  10-08-06 Ian Tyson Singer
  10-08-06 Wylie Gustafson Singer
  10-08-06 Dave Stamey Singer
 
  Western Theme Parks
Not real cowboy but a lot of fun for the kids
  09-03-07 New Jersey Wild West City
  10-08-06 Germany Pullman City (site in German) (slow to open)
  09-03-07 Airzona Rawhide, in Phoenix