You need a video capture device (a camera, or other USB device of sorts), a video feed (again either a camera, or if you have a video mixing board, the output of that) and you need a computer with an internet connection. You then need to set up a multi-cast streaming server.
This is the general idea:
Video feed -> Capture Device -> Computer -> Multi-cast server software -> The Internet -> People's computers
I'll edit this post later to recommend some software and hardware and such.
Jacob
EDIT: BTW, do you have a Mac? *crosses fingers*
EDIT2: Progressive streaming is probably the best way to go: read about it
here
EDIT3: Software like
this are designed to do all of the set-up for you, however, will run you somewhere around $40. They have a trial period, just to make sure you can get it working. I am not personally recommending this particular software, as I have never used it, but it seems like it might do something like you are looking to do.
Also, regarding video devices, if you already have an existing DV camcorder, you can simply use this, plugged into your computer. If you don't have a DV camcorder, but do have a regular camcorder, you can use the video/audio output, and feed it over long RCA cable (convenient for putting the camera far away from the computer) to a device like
this, which you can pick up from best buy for $50. I might note that I have used this device, and while it's not the best in the world, it does the job, and is usually stocked at local Best Buys.