Hmm... I figured there would be a Myth Busters thread out here somewhere but I searched and didn't find one.
Cool episode last night -- lots of big booms and excellent high-speed (super slow-motion) shots.
On the "Speed" bus myth though, a bus taking a very tight corner at 50 mph and not flipping over, I have to call BS.
First, from the footage, it looked like that after the bus made the corner, it do d not look like the bus was still going 50 mph or better. It looked like the speed had dropped down to about 35-40 mph. At this point (in the movie), the bomb on the bus would have detonated because the spedometer went under 50 mph. I know Jamie and Adam both were doing 50 when they entered the corner, but my guess is that they either took their foot off the gas pedal or kept it depressed the same amount while they went through the corner. Obviously, with the bus making the corner and skidding this would slow the bus down.
Secondly, after making the corner, both Adam and Jamie went off the coned-off "road". In the movie this would have put them off the road and into the ditch or somewhere where it would have been difficult to maintain 50 mph.
I enjoyed the show, though. It was funny when the car going under the semi-truck trailer had it's top sheared-off and the breaks failed and it flew over the earthen berm.