Putting this here for Google's sake -- the information is out there, but scattered...
You can play the High Definition videos from Apple's Quicktime Trailer site on your PS3 (maybe the Xbox 360 as well -- I don't have one to test.) This is nice, as Apple's trailer site has about 10x as many trailers available compared to the PSN store. The HD videos are internally MPEG4 conformant h.264 video and AAC audio. I believe Quicktime Pro is also required. In theory this should work in either OS X or Windows, but I only have OS X to try.
Click one of the links (depending on your TV's resolution, of course) and the trailer will load in QuickTime Player. Depending on download size, it will take anywhere from a couple of seconds to an eternity for the movie to finish downloading. I recommend allowing the trailer to download fully before trying to export it.
Keep it short for pithy sake.