Drupal Media + YouTube + WYSIWYG
Edit: Note that the module currently only works for Drupal 7. This set up requires the Media, Styles, and WYSIWYG modules (with the CKEditor plugin), and optionally Media: Flickr and/or Media: YouTube. Note that it's currently the dev releases of all those modules. /edit
Here it is with a YouTube video being resized in the WYSIWYG:
And the final node (note that it's inline).
And in a comment (this is a remote Flickr image, also available through the WYSIWYG and Media magic combo).
All of this is out of the box functionality! We're planning the alpha release any day now; just have to fix up a few things and get it stable enough. Join us in the #drupal-media channel of IRC if you want to help out next week!