Hulu is a new place to watch online TV. It is free service, but you need sign up to watch. Not like youtube, The TV show here have better quality, or you can watch at HD quality. You can't find all episodes to your favorite show, but they still have a lot of Episodes for to to enjoy. The Episodes is not up to date by real-time. Most of them are old episodes. Popular show are usually have more episodes.
They also have trails or clips for TV show, but I am not a big fan to watch clips of show.
Hulu has "CC" option for some episodes, or maybe all episodes. It is very help for people not use En as first language. I find this function are very useful.
HD program are not really help to me. My PC are old (IBM PIII 800), and board band are not so "Fast" where I work. So the show will become unwatchable.
In general, this is a good site to watch TV show.
Here I provide two rreference link, you can see other online TV station, and test your network speed. Inorder to get best result, good network connect is important to see online TV.