Pyro A/v Link
Possibly, but I've never actually done it before with a computer as the source. There are digital converter devices that can accept input from devices through S-video, A/V inputs, Component video output, and composite video. And the device would connect with the computer via firewire.
Try looking up 'Pyro A/V link' That's one device I've used before.
Just note that there are limitations to what can be captured. I believe DVD's are encrypted so you can't capture the input with this device. I don't know if Hulu has the same restrictions. If you can capture video, you use imovie to convert the file to quicktime and it could be used by itunes.