In fact, I haven't owned a TV set or paid for cable for a good two years now, but only in the last year have I really noticed this free-online-TV trend really picking up. It's a blessing and a curse, b/c it seems like I do everything on my computer these days: work, entertainment, etc. Don't go down this road if you're unprepared.
That said, here's a roundup of the best sites to watch your TV shows. Sadly, I haven't yet figured out where to watch all those trashy Bravo reality shows — Real Housewives of Atlanta, anyone? — but if anyone knows, my cultural understanding of the world would be much indebted to you.
— This is a site put together by NBC, but you can find shows from other major networks and even small cable networks here too: FOX, CBS, ABC, Food Network, etc. Most shows stream directly off this site, but if not, they will link it to the original. They also stream full movies here too.
— Good for watching Gossip Girl
and any other teen show. In fact, any network website will also likely stream their original shows online. ABC claims they were the first network to do this (and as far as I know, they're right). Even a premium cable network like Showtime does it for some select episodes.
— I have to highlight this particular network b/c they seem to syndicate a lot of older shows online here. For instance, did you know you could find the entire first four seasons of Beverly Hills 90210
here? Uh, yeah.
— This is simply an aggregation site that links you to other sites showing stuff. It doesn't always feel organized. Actually, I'm not sure if this one is legit, but it's more comprehensive than Hulu. One of my friends managed to watch an entire season of a British show before Showtime bought the US rights to it and aired it a season later.
— Yes, you have to pay for the monthly subscription service. I had originally joined for their original service (mailing me DVDs), but now they also offer instant online playing for certain select TV shows and movies too. I've had the best experience with their streaming quality.