Ffmpeg

[RUS] Видеохостинг своими руками / Видео в интернете / Хабрахабр

http://habrahabr.ru/blogs/video/111249/#habracut Article describing some quirks, tips and tricks needed for organizing proper HTML5 video hosting ( also see this ffmpeg profile http://pastie.org/1432128 )

HandBrake - Muti-platform open source video transcoder

http://handbrake.fr/downloads.php works on Win, Lin and OS X, based on ffmpeg