Brendan Eich, the Canada-loving technical leader of the Mozilla project, has written a piece on The Open Web and Its Adversaries and given a presentation on The Open Web. In addition to a general overview of what it means to have an open web, the post mentions work that Opera and Mozilla are doing with the WHAT working group to create new HTML tags for <audio> and <video>.
The basic idea (still in the early stages, I gather), is to create <audio> and <video> tags that would allow audio/video playback in the browsers without relying on a proprietary plugin (like Flash, in the case of YouTube). Browsers implementing the tags would be able to use any video format, but all browsers would support a base format of Ogg Theora and Ogg Vorbis.
Theora and Vorbis video and audio compression formats that are free, open-source, and unencumbered by patents. I’ve written before about the importance open formats for media.
If Firefox and Opera were able to leverage their combined corner of the market share and force Microsoft to implement such a setup in Internet Explorer (or if they did so eagerly on their own), it would be a great step forward for media on the web.