This user script adds a download menu to the watch page of YouTube videos.

Note: The download links lead to the stream URLs of the videos. Currently it is only possible to force a download and suggest a nice file name using Google Chrome (14.0.835.15 or newer). So if you click the link using another browser and it supports playback of the video it won't start a download but starts playback of the video. You have to use the context menu option "Save Link As..." in order to save the video.