Captify is a plugin for jQuery written by Brian Reavis (@brianreavis) to display simple, pretty image captions that appear on rollover. It has been tested on Firefox, Chrome, Safari, and the wretched Internet Explorer. Captify was inspired by ImageCaptions, another jQuery plugin for displaying captions like these.
The goal of Captify is to be easy to use, small/simple, and completely ready for use in production environments (unlike ImageCaptions at the moment). Also, it's only 2.3kb!