The type of crash pads you want depends on the level of the skater. For example, I have the knee pad from that website, Glacierskater, but, if you go into your jumps with a lot of speed, if they're particularly high, or if you're working on harder jumps, they ten to slide A LOT (I had this problem a lot when I was first working on triples). Sometimes, if you're only hitting one small part (I have scar tissue on my knee from a lot of falls before) all you need is a small pad (I use cosmetic pads, which, at about a dollar for three, are a lot cheaper than crash pads -- and they don't slip as much).
When I was younger I had a crash pad that everyone just referred to as a butt pad. I don't know if they still make them, but they went on kind of like a diaper (a little embarassing, but since everyone wore the, no one cared) so they didn't slide at all. After a while, my coach made me stop wearing it because she said I was losing the fear of falling that made me want to stand up, but until that point, it worked really well.
