My interest in MythTV has also sparked my interest in TV over the Internet. Many companies offer it “secretly”, for example movies on demand from cable operators in the UK are actually streamed over the Internet and loads offer small chunks of it. But are there any companies actually transmitting top content “live” over the Internet (free or subscription)? If it’s transmitted live (i.e. everyone receives the same thing at the same time), bandwidth some of the possible bandwidth problems can be mitigated with things like IP multicasting. And if you do have something like MythTV recording it for you the problem of people not wanting to see things at the same time go away too. Well to answer the question (there was one), yes. Unfortunately for the most part they aren’t the big channels, but there are quite a few for niche areas and some countries even make their government subsidised national station available.
The first site I found for this was wwITV. They list quite a few live channels and loads of sites that offer clips. But unfortunately many of them are out of date and just return 404s. An alternative for sources of web television is tVadio. They’re newer and don’t have as much (and seem far less international) but at least the stuff they list actually exists and is of a reasonable quality (well whether you like the actual transmitted content of the channels is up to you :P). The sites listed though still only represent baby steps on the path towards true Internet television.