Not many places at the moment, since only Safari and Mobile Safari for iPhone and iPod touch support it. It's supposed to become a standard later on, which I'm hoping for. If you're ever able to see what the 3D transforms can do, it's actually really cool that it can be done without the use of something like Silverlight or Flash Player (which both suck if you don't use Windows, and SL isn't even available on Linux proper).
Just something we had to dig into at uni. Experimental web standards, their impact, and showing one being used. I made a little thing where text revolves on a merry-go-round, with the haunted merry-go-round music from Super Mario 64 playing in the background.