there are several applications out there that will download/extract the youtube video and than will convert it to an iPod friendly format. Off hand I do not know their names as I dont use youtube but I know they exist.
on a mac, open the activites window while at the youtube page you want. double click the link for the largest file on the page (it will contain get_video in the url). convert the file "get_video" (in your downloads folder) with iSquint. tada! no shareware thank god.