A while back it was announced that Daily Motion, an online video site, had opened an OLPC channel for sharing videos encoded using Theora for playback on OLPC's.
The channel, http://olpc.dailymotion.com, contains theora videos aimed at the OLPC audience. What's nice is that the videos playback in Firefox 3.1 using the native Theora support and don't require a plugin, for example this video.
Looking at the Daily Motion page it seems they use the <object> element to playback the Ogg Theora file, which uses the internal decoder and player user interface. This is a nice result from the adding of support for direct loading of Ogg files that Robert worked on.