YouTube HTML5 Beta →

If you use Safari or Chrome, you can opt for YouTube to use the HTML5 video tag instead of flash. Excellent.

Update: Vimeo have also launched an HTML5 beta, on a per-video basis. Both are using H.264, which could well sound the death knell for Ogg Theora, and have an impact on Firefox’s future (as I understand it Firefox can’t support H.264, because the patent license required is incompatible with its open source license).