There must be many tools to see or search youtube videos but no doubt iDesktop is the best.
With iDesktop you can not only search your favourite videos, see the thumbnail of each of them, play the videos but also download them easily. It also enables you to convert the videos in any format be it wmv, mp4, mov, 3gp and avi etc. Needless to mention, the conversion takes only seconds for the entire work.
iDesktop is easy to use and also saves lots of time while playing and buffering the videos as compared to the normal youtube site. Whats more, you can also personalize it for better and comfortable experience.