The private pilot was at the airplane controls during the landing approach. Another private pilot was present, and acting in the capacity of a safety/lookout. The pilot held the airplane in a yaw during the landing approach, while the safety pilot looked through the rear window in order to monitor another airplane, which was just behind them. The safety pilot became concerned that the airplane behind was flying too close, and watched as it overflew their position during the flare. He then looked forward and noticed that the airplane was still in a yaw condition, and not aligned with the runway centerline. The pilot attempted to correct the yaw during the flare, but landed in a side load condition on the left main landing gear, and the airplane subsequently veered off the runway. The safety pilot attempted to take control of the airplane, but it continued into the ramp area and collided with two parked aircraft. The airplane and one of the parked aircraft sustained substantial damage during the accident sequence. The pilots reported no preimpact mechanical malfunctions or failures with the airframe or engine that would have precluded normal operation.