The PS3 does not play Quicktime .mov's...I wish! Quicktime is the gold standard for movie trailers. Apple needs to get in bed with Sony on that. But they won't, cause they want us to buy AppleTV's...
As a Mac user, I use VisualHub to convert any videos for my PS3. Use the "MP4" tab, with "H.264 Encoding" checked...it's a long process though, depending on the video length and how fast your computer is.
Another option is streaming content to the PS3, I use MediaLink from Nullriver. They are supposedly working on adding 'transcoding', this would allow converting any video formats on the fly, as opposed to converting them first. I hope that update comes asap.
I was going to recommend stage6.com, but looks like it's no more. It was home to tons of DivX content, that should playback on the PS3 without converting. Unfortunately it's not a format I've seen a lot of mainstream media companies use, even though millions of Internet users use it.