jQuery Retina Display Plugin

The jQuery Retina Display plugin will substitute high resolution versions of your images (if they exist) for high resolution displays (such as iPhone 4) only.

This plugins requires no client-side changes , other than the inclusion and initialisation of this plugin. If the 2x image doesn’t exist, the standard resolution image is displayed. This allows for selective addition of high resolution images.

via jQuery Retina Display Plugin | Troy Mcilvena.