At
www.justin.tv/directory/sports
AFAIK is legal (altough I'm not sure, they haven't had legal problems that I know).
The day of the race you have to connect "early" (there is a limit to the number of people connected). I use it to watch the practices (which are not shown on my cable).
Right now (and always, it seems) you can find a channel called F1 Legends, where they show old races.
If you want a really good history of F1, on DVD, send a PM to our appreciated member, Chaparral, in this forum. He has a company devoted to produce movies, and it has produced a very good series (A Gentleman's Motor Racing Diary). The name of his company is Capricorn Media, google for it if you wish (sorry, Chap, I won't post commercial links).