The pilot reported that after landing and after turning left onto the taxiway, "the engine slowed." He then added power to keep the airplane turning to the left, but experienced very little braking on the left brake. The pilot stated he believed that at about this time he may have gotten the heal of his left foot over the right rudder pedal, which rendered his attempt to turn [left] being unsuccessful. Subsequently, the right wing of his airplane contacted the right wing of a parked airplane, which was facing the opposite direction. The right wing was substantially damaged. A postaccident examination of the airplane's left brake revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.