Hulu.com
Just finished watching the pilot episode of Firefly as I never saw the series when it was on. All kinds of TV shows and movies can be found on the site. The full screen feed is pretty nice. I watched it on my HDTV and it looked a lot better than the feed from NBC's site.
From their "about" section
Hulu's ambitious and never-ending mission is to help you find and enjoy the world's premium content when, where and how you want it. We hope to provide you with the web's most comprehensive selection from more than 50 content providers including FOX, NBC, MGM, Sony Pictures Television, Warner Bros., Lionsgate, and more to deliver premium programming across all genres and formats, television shows, feature films, and clips. Watch full-length episodes of current primetime TV shows such as The Simpsons and The Office the morning after they air, classics like Miami Vice and Buffy the Vampire Slayer, and clips from Saturday Night Live, Nip/Tuck, and others. Hulu also offers full-length feature films like The Usual Suspects, Ice Age, Three Amigos!, and The Big Lebowski as well as clips from films such as Napoleon Dynamite, The 40 Year Old Virgin, Devil Wears Prada and many more. Hulu is free and ad-supported — available anytime in the U.S.
Hulu was founded in March 2007 and is a joint venture owned by NBC Universal and News Corp. In addition, Hulu has closed a $100 million investment from private equity firm Providence Equity Partners.
Hulu's small, but growing team is headquartered in Los Angeles, California with a Research and Development team in Beijing, China.