Just like I mentioned some time ago,
I like mplayer a lot. It is not a secret that you can not only just decode various media (watch video and listen to audio), but also encode (create your own video/audio files, rip DVD) just the way you want. There is even
a port of mplayer for Windows, so that people that have made a mistake in choosing their OS don't have to suffer :).
Mplayer works exactly the same across a number of OSes, so my instructions that follow will work pretty much anywhere...