YouTube, Picasa, Flickr and Yelp previews in your Gmail

Official Gmail Blog: New in Labs: YouTube, Picasa, Flickr and Yelp previews

just send the links of
1. YouTube,
2.
Picasa,
3.Flickr and Yelp previews in your Gmail to your friends in email
and then can see the preview before opening the linbk in thier gmail mail