http://www.webmproject.org/ WebM is an open, royalty-free, media file format designed for the web.
* VP8, a high-quality video codec we are releasing today under a BSD-style, royalty-free license
* Vorbis, an already open source and broadly implemented audio codec
* a container format based on a subset of the Matroska media container
Mozilla, Opera and Google are behind WebM, even IE9 will have support if the VP8 codec is installed.