I second the Quicktime Pro registration. QT Pro ROCKS. It's got SOOO much stuff in it, it's amazing. It's worth it for just the codecs it includes (Sorenson 3, mpeg4, Cinepak, etc etc).
You can save any QT capable clip (mov, mpg, avi) without having to dig for it in your cache or HTML source code.
It included filters, export features for almost any image format.
I can't live without it.