Apple ProRes QuickTime Decoder!
Apple Pro-Res is a great format for editing, but it use to have the disadvantage of not being readable on a Mac that doesn't have Final Cut installed. When I needed the video files to be reviewed by someone who doesn't have Final Cut before the final editing, I had to convert the videos to something like H.264 and that took a long time (even on my Quad!). Apple solved everything in August with the release of Apple ProRes QuickTimes Decoder. It is a plugin for both the PC and the Mac version of QuickTime and it lets computers without Final Cut play videos encoded with ProRes. Apple doesn't publish system requirements, but playing HD video requires a powerful computer (dual core or better). More info and download link here.