The way camstreams use to work was that you installed an encoder, they have one of their own, or I used Windows Media Encoder (free download).
The encoder takes the camera feed and sends it to camstreams. They turn around and provide the stream that other people see. It's buffered so it lags about 20 seconds or so behind the actual feed, but it's a nice steady stream in real time. You are allocated a certain amount of bandwidth, I had 1.5 mb's, then based on the quality you want to stream (and whether of not you include audio which adds to the bandwidth), that's how many people can view your stream. So if you have 1.5 mb total, and you stream 256k, 6 people can view the stream at once. I use to get 10 or so at once on my stream.
It's a little different than Wunderground because it is a steady continuous feed, not something that's sampled periodically.