The pilot reported that, as he approached the destination airport, he maneuvered the airplane to adjoin the left downwind. He noted that there were numerous airplanes in the traffic pattern and opted to perform a short approach to expedite the landing. The pilot did not remember if he performed his normal landing checklist but did remember that he did not follow his usual procedure of initiating a go-around if the landing gear was not assured to be down and locked. The airplane touched down with the landing gear retracted and slid off the runway surface into a berm. Both wings were substantially damaged. The pilot reported that there were no mechanical malfunctions or failures with the airplane that would have prevented normal operation. The landing gear handle was in the down position, but he could not remember when he selected the gear down.