jQuery Fitpic 0.0.5
A jQuery plugin for responsive background images
While the same effect can be achieved via CSS3's background-size: cover property, that method leaves blank spots when the browser is resized to various aspect ratios that don't coincide with the photo's aspect ratio.
jQuery Fitpic fixes this problem by constantly calculating and resizing the image, so none of its dimensions are smaller than the viewport size.
A simple demo is included with the download package.