BlogExpat allows you to easily embed videos in you articles.
The video can be inserted via a popup window (button YouTube in the edit form for posts) where users can type the video page URL (like http://www.youtube.com/watch?v=-8GoJw-7Q7Y&mode=related&search=) or the movie URL http://www.youtube.com/v/-8GoJw-7Q7Y)
On top of this, users don't need to worry about XHTML compliancy as the plugin will generate the right code using only <object> tags.
Here are a few examples:
It is a bit more complicated. You can either edit the article in HTML and past the embeddable player code displayed on the video page, or, easier, you copy within the embedded code, only the URL after <embed src=".
Then you insert it into the popup window (use YouTube format for example).