Changing the position of the background image felt to be the best approach to creating the type of effect we're looking for (and I'm not the first to think so: see the examples at the end of this article).

jQuery is a great library for this type of task but out of the box, it can't animate background position properly because of the need to animate two values instead of just one (too bad not all browsers implemented the non-standard background-position-x and -y like Internet Explorer). Grab the latest version (1.0.2 as of this writing) of the Background-Position plugin.