If you have ever visited the web site of any of the major (or minor) TV networks you have discovered that they are beginning to make some of their past broadcasts available there. If you have a broadband (cable, DSL or FIOS for example) connection to the Internet from a computer less than five or so years old you can see shows that you might have missed or that you want to see again. All episodes of a very few shows might be available while others are missing completely or have a few recent shows available. To find this, you have to go individually to each networks site and hunt around. Now there is a better way!
I discovered this gem from a great article in the September 2008 edition of Wired Magazine and last night I watched a gem of an episode from a late 50's early 60's Western series (the hay day of the TV western) called "Have Gun, Will Travel". Fantastic! Hulu has struck deals with many (but not all, don't look for Oprah for example) networks and many film distributors as well to act as a hub for hosting and/or locating their content on the WWW. Enjoy!
Oh, and for a more recent development on the same topic, it looks like YouTube is now hosting and presenting widescreen HD video content. Now to view this you will need a high end broadband connection and a very recent medium to high end PC. Check out this example on YouTube. Give it a go to see if your broadband connection and PC are up to it.