Veodia seems useful, as far as I can tell from the 500 minutes (viewing, per month) and 500GB of storage they provide for free. It uses a browser plugin to get audio and video from a camera (iSight or DV camera, for example), provides both HTTP and RTSP live H.264 streams, and stores a recording on their server that anyone can download or view later, embedded in a web page as QuickTime or Flash.
The RTSP stream can be embedded in Second Life as a video wall - unlike QuickTime/Darwin Streaming Server you don't have to worry about firewalls or hosting multiple streams. Zee Linden used this last year, for a presentation that was recorded and is available on YouTube.
I'm hopefully going to give Veodia a proper test at the TalkScience event at the British Library next month.
Update: apparently Veodia aren't working on public video streaming any more - they're concentrating on enterprise products for internal use - so that's out.