jQuery Sequency is a jQuery plugin for before/after image comparison on scroll.
before-after.js is a simple and responsive image comparison slider.
Before and After is a jQuery plugin to view an "after" version of any image as an overlay of the original one.
A draggable handle bar lets the user decide how much of each image he/she wishes to view. The "before" and "after" slides can each contain not just a main image, but other HTML as well, such as a caption.