Simple, Responsive iframes.
jQuery mediaWrapper is a plugin for wrapping and making iframes and embedded videos behave more like images when developing a responsive website. Currently iframes will default to an arbitrary width set by the embed code, just like images. Unlike images, the max-width: 100%; height: auto; technique doesn’t work. mediaWrapper.js helps solve this problem by providing a wrapper that enable iframes to work responsively.
Check out the plugin over at GitHub.