The pilot reported that, during takeoff, everything appeared "good" and then he saw a yellow warning light illuminate. He remembered seeing the letters "hydr…" on the light and became concerned about the landing gear. He decided to abort the takeoff and reduced power and held back pressure on the yoke but the airplane became airborne momentarily. He intentionally "let" the airplane go left over the grass. As the airplane decelerated, he saw a taxiway sign ahead, the stall warning horn sounded, and the airplane settled back onto the ground on the taxiway sign. He pulled the yoke full aft, added right brake, and the airplane impacted a ditch. The pilot reported that before the flight he performed weight and balance calculation. He added that the airplane was in excess of 300 lbs. over the maximum gross weight and was "heavy aft." He reported that he had 7 persons on board the 6-seat airplane, with a person sitting in each seat and one additional sitting on the floor. The airplane sustained substantial damage to the right wing. The Federal Aviation Administration inspector reported that evidence and testimony showed that, during the takeoff, the left wing and nose wheel lifted, and the pilot lost directional control. The airplane veered off the runway, collided with a sign, crossed a taxiway and a ditch, and stopped in front of the terminal parking area. He added that, during a postaccident examination, no warning lights were noted. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.