You can embed third party content (like YouTube or Vimeo videos, Google maps, Flickr images etc.) right into a Joomla module or article without any extra plugin, module or other extension.

BUT there are two major problems doing it::
1. The default editor removes some HTML tags like OBJECT or iFRAME
2. Even if the Super Admin adds content it will be checked against a blacklist and HTML tags which can caused security problems will be removed automatically, too.

If you try to copy&past some code Joomla will remove it automatically as soon as you save your changes.

The solution:
Turn off the default editor
1. Click on "Site -> My Profil" in your Joomla backend
2. Select "Editor - None" as Editor
3. Save the changes

Disable the text filtering for your Super Admin
1. Click on "Content -> Article Manager" in your Joomla backend
2. Hit the "Options" icon in the upper right corner
3. Select the "Text Filters" tab in the options popup window
4. Select as "Filter Type" for you as Super User "No Filtering"
5. Save the changes

Now you can grap the "embed" code from YouTube, flickr, Vimeo etc. and past it right into an article or custom module.