Whole suits of leathers are excellent. I was on the back of my mates bike when he did a wheelie at about 40mph and I fell off the back and was sliding down the bloody road on my arse. Other then it getting a little warm around the bum I was fine and got up and gave my mate a right rollocking as if it hadn't happened. Totally bolloxed up my helmet though (remember that if you so much as scratch your helmet that it's advisable to replace it - My instructor had me bring my old one in and had a look at it and then showed me why... he tapped it with a hammer and the bloody thing split in two).
Yeah I think I saw a vid of a dude talking about how damaged Helmets are completely useless. Even if there's a small dent on them.