Here’s a quick and easy solution to prevent youtube videos from overlapping WordPress menus. Simply add this bit of code to the youtube URL &wmode=transparent
For Example: <iframe width=”420″ height=”315″ src=”http://www.youtube.com/embed/0Bmhjf0rKe8?rel=0&wmode=transparent” frameborder=”0″ allowfullscreen></iframe>
To see how this works in action just scroll down!