The WordPress theme that I’m using uses the Foundation framework from Zurb (located here). But one thing it didn’t seem to do so well was the embedded videos from youtube. Sure they would show up, but once I started trying out the responsiveness, it would remain at a static width. It would break things, but it was ugly.
Here is a great little solution from the peeps at Zurb. Responsive Video.
For more information on Foundation, the responsive framework. Click here.