Instal the Drupal module called embedded video from http://drupal.org/project/emfield

After that, add this field to any content type you wanna put into. (Addr: /admin/content/node-type)

Select Manage field and then add a field called embedded video.

After that, every node created using this content type contains an embedded video field. Simply copy the youtube link like http://www.youtube.com/watch?v=K7KhcEAmCxQ&feature=related and the video can be shown. It does save steps in copying object tags to display youtube videos.

You can check what type of video could be embedded in /admin/content/emfield. Configuration can be as well done there.

PS. Not only video can be embedded, even flickr or other kinda media can be embedded. This can be achieved by enabling Embed media module from /admin/build/modules.