Well, the website here will let you download the YouTube video as a .FLV.
You can then you use the free version of iSquint to convert the video to any format you prefer, probably .m4v for your Touch. Then you can just add the movie to your iTunes library, and sync!
GetTube downloads them without having to go to a site since sites dont work half the time, but it also converts it to mp3 or mp4 so you can put them straight into iTunes and straight on your iPhone/Touch.