mashface.net
This is something a friend and I made because we where frustrated at how limited youtube doublers and the like are. It gives you as many light boxes as you want which you can resize. The boxes can take youtubes, images, mp3s and html. The boxes can take css rules and other content specific rules depending on the box's url. eg. If the box holds a youtube you get a loop rule.
Some examples:
http://mashface.net/#/w3rews
http://mashface.net/#/m3ik2g
Chrome only sorry.
http://mashface.net/#/m3ik2g