I saw a really cool photo slider on http://killinglincoln.nationalgeographic.com/ that allows the user to slide a bar in the middle of two photos that were of the same ojbect just many years later and you could see the difference between the two. Any ideas how this is done? I assume it was flash because the whole website is built as far as I can tell in flash. I'm in the process of creating a website with some of my students that shows the progress of our small town and this effect would be icing on the cake. Any help would be greatly appreciated.