After an instrument flight rules cross-country flight, the pilot received multiple radar vectors from air traffic control for traffic and after mis-identifying the destination airport for a visual approach. He then had difficulty identifying the runway while looking toward the setting sun and setting up the GPS to identify a 2-mile final approach to the runway. On final approach, he was paying close attention to departing traffic on the landing runway and stated that he configured the airplane for landing but neglected to lower the landing gear. He heard the landing gear position warning horn and realized that he had forgotten to extend the landing gear when the airplane settled onto the runway. The airplane skidded down the asphalt, resulting in substantial damage to the fuselage. The pilot reported that there were no mechanical malfunctions or failures of the airplane that would have precluded normal operation.