http://www.webmproject.org/ http://openvideoalliance.org/2010/05/google-frees-vp8-codec-for-html5-the-we... http://www.h-online.com/open/news/item/Google-open-source-VP8-as-part-of-the...
Container will be .webm, a modified version of Matroshka. Audio is Ogg Vorbis.
YouTube is serving up .webm *right now*. Flash will also include .webm.
Comment from WMF already, that WMF is happy to host any free codec. Encoders are available at the project home page.
- d.