How can I stream live, full-screen video? What equipment do I need?

I have found many services advertised online offering the streaming servers, internet bandwidth, etc. but I want to know how to do the whole thing myself without going through a special service. I have access to very high speed broadband internet already, I have good professional video cameras, but need to make the conversion from the camera feed to the internet stream, LIVE (a few seconds delay for encoding is acceptable).

If you think a computer with the right software will do it, please give the specs, since my computer does not appear to have sufficient horsepower for a full 720 X 480 resolution stream at 30 fps (anything above 1400 kbps bitrate). I would prefer a stand-alone device (not using a PC).

Also, I would accept any format commonly used and which can be played on the average PC, such as WMV, MPEG2, MPEG4, Real, AVI, etc. To be able to multicast and to stream at multiple bitrates simultaneously is preferable.