My favorite FF add on is DOWNLOAD HELPER, pulls video streams off most internet sites clean as a whistle and will even do file format conversions in the background to most major formats incl
MPEG-1 or 2, WMV, QT, MPEG-4 AVI, DV-AVI and a few others.
On the little computer (a single core 64 bit AMD running XP) the conversions take a couple of minutes for every minute of video.
On the main editing workstation the conversions are completed almost as fast as I can press the damn button!
There ARE one or two well known sites that it wont work on.
Hulu defies attempts to download streams, at least for me. None of the add ons I have tried will do it.
I've managed with a screen capture tool but less than thrilled with it.
I am sure that I could connect an analog capture card and play the video output into another analog card and get anything I want that way. There's more than one way to skin a cat of course.
Still, I am amazed that FF add ons like DH work so well.
I remember when it was amazing to get ASCII art!