Just read on 9 to 5Mac that VLC 2.0 from VideoLAN was announced, and includes some cool new features, including support for Blu-ray (not burning, apparently), fullscreen in OS X Lion and more. Check out the details and see some videos of the new UI on 9to5Mac.com. It’ll be available for Mac, Windows and Linux at their site, in the very near future.
I use VLC a little bit, mostly to see raw XDCAM EX files without having to open up the Sony XDCAM clip browser or Final Cut Pro X.