There was also a 727 that was involved in an uncommanded unilateral slat deployment over Michigan sometie during the '60s I beleive. It took a nose dive and fell about 30,000 feet before the pilots recovered. It likely broke the sound barrier on its way down - but survived.
Also, I heard a rumor that the P-38 might have been the first aircraft to break the sound barrier, not the X-1. During terminal-velocity dive tests for the plane, one pilot pushed teh envelope a little too much and lost control. He recovered, but the speedometer was stuck at a speed that would have been above Mach 1 for the altitude where he lost it. But nobody knows for sure so Yeager still has the definite credit.