Ogg

Ogg is a free, open standard format for music, video and other multimedia. It is run by the Xiph.Org Foundation. The Ogg format is unrestricted by software patents and is designed to provide for efficient Internet streaming and for editing of high quality digital multimedia.
The project was based on the popular AVI and Ogg formats, which at the time only supported audio. Some time ago, the OGG Vorbis format was created to change the mp3 format. To store the vorbis audio stream, the OGG Bitstream standard was developed, which was later used to store video.
Recently a big library on the internet, the Internet Archive, announced that they are going to convert many videos and other multimedia to the Ogg format as well as other formats like the proprietary Adobe Flash flv format.