You can embed and programmatically control multiple YouTube videos by putting onloads like the following in (existing) iframes:
This will only work if we have this in the head:
and if the video-url in the iframe contains html5=1 (IE-requirement) and enablejsapi=1.
View source for further info.
The YouTube ads don't display if the width of the iframe is less than 320 pixels (the iframes to the right are 319px wide).
The YouTube API reference for iframe embeds is here