There are many different YouTube URL formats and they often include information about playlists, referrers, etc. A few examples:
http://www.youtube.com/embed/T6DJcgm3wNY?rel=0
http://m.youtube.com/#/watch?v=T6DJcgm3wNY&feature=player_embedded&desktop_uri=%2Fwatch%3Fv%3DT6DJcgm3wNY%26feature%3Dplayer_embedded
However, when I want to share a YouTube URL with someone I only want the basic URL that points directly to the video. In this case:
Here's a workflow that takes any* YouTube URL and copies the basic URL to the clipboard.
Download: basic-youtube-url.alfredworkflow
* It might not cover every possible URL format, but so far I haven’t come across one that doesn’t work.