Video related links
There are loads of people trying to do this sort of stuff, here's a few links to the ones I've found most interesting:
Microsoft provide a free download to enable Quicktime to play WMV files on a Mac.
This guy used DSS to let his family view his wedding video, and used free tools to do it. Here's how (includes some mencoder and ffmpeg usage examples).
MPlayer is great but highly difficult to use. Here's a few tricks that someone else has written up.
This guy did all the hard work so I didn't have to. In return I told him about the Windows/Mac line-break thing.