How can I watch TV on internet for free without buffering?

You cant. Buffering is needed to load enough of the video so it doesn't stutter.
Especially off the net. Some site work better and faster than others. Like nbc's site is pretty good... loads fast.. very short buffer if any.

I've watched many episodes of Lost on the ABC web site with no problems. Hulu.com also has quite a few TV shows available and I haven't seen a lot of problems with their buffering.

It's not just the quality on the web site's end - if you have a bad or slow connection on your end, that will affect the quality of your viewing experience.

Vasily