There are a few things that will work for a cam. But like CashAddict mentioned, it depends on how many people are watching. 2 programs that spring to mind are Emulive, and Media Player. I think those are the largest.

With media player I believe you need the MP Server. Emulive was pretty good, stable, and you can stream audio and video. However, if you save the clips to stream at a later date you can only use them in the emulive applets. They may have added new formats by now. The price wasn’t bad, but you could only lease it per channel. (I think we paid about $1000 ever 2 months for 4 channels.)