I am particularly found of the
TubeHunter program because you can download videos from a myriad of video-sharing websites very easily as well choose what format you want to download it as. There are also extra features such as a video converter, an iPod video converter, and a DVD ripper.
So you can download Youtube videos, save it as a .wmv, .mov, .avi(divx), .mp4, and much more, decide to convert it later on to suit your needs, then you can watch them on the go on an iPod or similar portable video player. Truly awesome and the ease of use is amazing!
But I think you might have to purchase it, otherwise you are stuck with a free trial version.
I bypassed that obstacle..by...um... some unscrupulous methods.
But I highly recommend it.