Local blogger Matthew Kirschenbaum has announced the release of Virtual Lightbox 2.0. It's a free and open-source application that:

is an inline browser applet for image comparison and manipulation. Users can import images into the applet’s display area, arrange them in any configuration simply by clicking and dragging, magnify them, and apply basic image processing. The Lightbox will be of potential interest to anyone presenting images on the Web in a context where active comparison—what John Unsworth calls a “scholarly primitive”—is desirable.

There's a screenshot that gives you an idea about how this might be used. Slick!