Google Now Lets You Embed Videos In Your Email From YouTube

Enable YouTube previews, and you can watch YouTube videos from inside your Email:

Google has also been testing a feature that automatically turns direct links to YouTube videos copied into the instant messaging application Google Talk.

You can learn more at the Google Blog here..

http://gmailblog.blogspot.com/2009/03/new-in-labs-youtube-picasa-flickr-and.html