Pretty cool, huh?
But does more than just work with those few video sites. You can also add a video to your playlist from inside Safari. All you have to do is email the webpage to your account with SkyFire Video. You can also add a bookmarklet to Safari that will do the job. I don't think it actually copies the videos; it looks like the app is just a tracking system and video player. But it can help you build a playlist of videos for watching later.
You can get the app now in iTunes for both iPhone and iPad.