Ustream is website that offers the ability to serve out a network of live streaming video over the internet. This site provides web-based software to allow anyone who has access to video and/or audio feed equipment to easily connect to their site and start broadcasting over the web.
Another useful tool that Ustream provides is the ability to record your session. In case you wanted to have a video archive, your content could be recorded and accessible via the Ustream website.
In the BBverse, Ustream is no longer the preferred tool used to stream live recordings of the BBLiveShow and the NSFW after show and as of August 10th 2010, the pre show and after show have switched to justin.tv.