Are you looking for webcasting or webconferencing? I've also been researching inexpensive webcasting options.

If all you want is one-way audio-video so people can see and hear what's happening in the room (i.e., no screensharing or live conferencing), then there are a handful of free youtube-like sites that are designed for live video:

http://justin.tv
http://ustream.tv
http://mogulus.com
http://stickam.com

I haven't tested them all yet, but have played a bit with justin.tv and it is REALLY easy to use. You simply turn on a webcam, go to the website and click the big "broadcast" button in the corner. You can get higher quality by using Adobe Flash Media Encoder for Windows or Quicktime Broadcaster for Mac instead of the site's more basic web-based broadcaster, but if you broadcast in H.264 it doesn't archive your video so you'd have to record it and upload it separately to a video sharing site after the fact if you want people to be able to watch the video after the meeting occurs (the web-based broadcaster automatically archives your "episode" so people can retrieve it on-demand afterwards).

When I tried justin.tv, there was a delay of a few seconds, so you won't be able to use it as a live conferencing solution, even with a telephone conference call (if users are both dialed into your conference call and watching on justin.tv, the delay in the webcast's audio is going to throw them off, and eventually create a feedback loop if their phone picks up the webcast's audio). But for a simple, one-way a/v webcast, it seems like a great, free solution. The others look promising, too, although some seem more complex (particularly mogulus).