Copying directly from playogg.org:
I'm writing today to ask you to support the Play Ogg campaign (http://playogg.org).
Are you tired of constantly being prompted to download proprietary software and plugins to play the videos and listen to the music you want? Are you fed up with seeing new gadgets that only use incompatible and restrictive audio and video formats? Did you know that it's not a lack of technological know-how that causes this, but software patents and other legal restrictions?
Increasingly proprietary software companies like Microsoft, Apple and Adobe are pushing video and audio formats that restrict access and restrict software developers, but there is an alternative that can be played on all computers without restriction—Ogg.
Ogg provides professional grade multimedia formats. Ogg is used extensively by free software projects, artists and a growing number of music and video distributors.
Soon over a million children and their families will be receiving the One Laptop per Child XO computer designed to play and create Ogg files. By advocating now for Ogg we can help ensure that those children will gain access to, and not be unnecessarily restricted from thousands of educational resources and materials on the web.
Join us in advocating for Ogg right now by taking 4 Easy Steps: Install VLC multimedia player, sign-up for the PlayOgg advocate mailing list, find and share Ogg friendly sites, and put PlayOgg Buttons on your web site or blog. After all that, if you are still looking for more to do, consider encouraging others to do the same.
Start here: http://playogg.org/
OGG Vorbis/Theora & free software FTW! (And NO DRM! ;)
OGG = Data container, Vorbis = Audio codec, Theora = Video codec.