I am helping setup streaming for trainings, with others asking about doing it, I decided I should add this to my blog. Here are my links for streaming and webconferencing. I list the webconferencing link here to explain the differences I see. Some of the webconferencing I have found doesn't support video or support having an adjustable size video window (dimdim.com). Webconferencing does normally have the capability to share presentations, like powerpoint. dimdim.com seems like a nice solution if you don't need to make the video window real big.
I will give more details about what we have done in future posts.