At 13:30 central time, a Cessna 172S lost most of one propeller blade during takeoff from St. Cloud Regional Airport. The separation occurred at 400 to 500 feet above the runway and the CFI was able to land the airplane on a parallel taxiway without incident. The airplane was damaged by vibration as a result of the propeller separation. Inspection of the airplane revealed the McCauley propeller blade separated at a point approximately 8 inches from the hub. The airplane had a total time of 236 hours.