I've been asked by a number of people to recommend different YouTube video download tools. Since I haven't tried them all out, I can't really give an answer. However I have come across the following website which has a comprehensive list of the tools available.
I don't know which of the tools listed on this site works best, nor which ones have been disabled by YouTube/re-activated by their writers. So I guess it's a question of trial and error and experimenting.
Graham Majin is Head of Video Marketing & Video Production at Kent video production company Kersh Media KWIKVID http://www.video-podcasts.org.uk

YouTube Downloader; No Flash Video Found - Alternative Download Tools