yeah, this is how i download the videos and save them to my ipod. lets say you wanna get this video
http://www.youtube.com/watch?v=Dx5ZjW4ukM8
to save it you wanna remove the "watch?=" (in red) and leave the "v" still in the link and just add a forward slash (/) after it so now that link should look like this
http://www.youtube.com/v/Dx5ZjW4ukM8
once you do that enter that on your browser and go to that address and it will play the video again but this time it will take up the whole page.
now notice the link of the video is different then what you pasted to see it. you will now see this
http://www.youtube.com/p.swf?video_id=Dx5ZjW4ukM8&eurl=&iurl=http%3A//sjl-static6.sjl.youtube.com/vi/Dx5ZjW4ukM8/2.jpg&t=OEgsToPDskLf4Vd7YqfHdARbZhDQ7LI8
now after the youtube.com/ you see "p.swf" (in red) you wanna change that to "get_video" so the link will now look like this
http://www.youtube.com/get_video?video_id=Dx5ZjW4ukM8&eurl=&iurl=http%3A//sjl-static6.sjl.youtube.com/vi/Dx5ZjW4ukM8/2.jpg&t=OEgsToPDskLf4Vd7YqfHdARbZhDQ7LI8
once you change the p.swf to get_video on the url click go or enter and it will ask you to save a flv file, once that is saved just convert the file into an mp4 file, i use videora to convert the file.
then you will have video saved to your hard drive. if you need more help let me know