Bittorrent has become pretty popular as an efficient, decentralized way of distributing large files, and now the same technology is being applied to streaming. P2P-Next is working on an experimental .tstream format
that will share streaming video using a minimum of bandwidth. It works like a regular torrent -- users who have part of a file 'seed' it for download by other users -- but with a twist. Each user grabs the blocks of data that make up a video just before they need them to play the next minute of content, upload it to the next user right away, and then "undownload" it.
The undownload functionality turned out to be the key breakthrough for this project, since part of the appeal of streaming is that you don't have to keep a massive file on your hard drive all at once. The Tstream format has a little help gaining widespread adoption: one of the organizations currently testing it is the BBC. If you want to try it for yourself, check out this trial run
of SwarmPlayer. Windows and Linux versions are out right now, and the Mac version is due next week.