The BBC has given the go-ahead for its Video-on-Demand services, due to be launched later this year. About 15% of total BBC content will be made available for download up to 7 days after broadcasting. You will then have 30 days to watch the programme. The BBC have developed their own peer-to-peer software and download manager (called iPlayer) to enable file-sharing thus avoiding costly server capacity.
More can be read on the BBC website
What isn't clear is whether this service will be available to people outside the UK, though I very much doubt it. At the moment many BBC live streams and download are only available to UK IP addresses. I am certain someone will come up with a way to get round the IP issue eventually, though (like perhaps proxy servers), so this might be of interest to many people without satellite TV or PVRs.
iTV is also planning to launch a similar service allowing people to download shows fromt he previous 30 days direct from their servers.