One solution which worked fairly well for us, we used Windows Media Encoder to stream the audio and video. You can share your desktop as well but it requires an additional stream. As the name implies, it only runs on Windows OS. We used Primcast as the streaming server. Accounts start at $13/month for 5GB of data which was plenty for what we needed. The bandwidth used was about 100MB/person for about 2 hours. For a camera we used a Logitech QuickCam Orbit AF. This is a nice little webcam the Windows driver supports auto-tracking, so that as the person on which the camera is centered moves the camera follows them. Occasionally it has to be adjusted manually to keep it tracking. For audio we are using high-quality wireless mics, one for the main speaker and another for those in the local meeting to participate and be heard by those streaming. To be able to get the two mics connected into the one input on the computer (so that we don't have to setup a mixing board for every meeting) we use a stereo splitter, so that one mic is the right channel and the other is the left channel on the computer input.
We use Yahoo! IM for those receiving the stream to give feedback.