Google Earth v5 has new features that gives you access to the past. I have used it to view the areas around Banda Aceh, Indonesia where the great tsunami (Dec 26, 2004) hit hardest. The images below are of June 23, 2004 (6 month before the disaster); Jan 28 (1 month after), 2005; and Feb 23, 2009 (recent image). As a matter of fact, Google Earth always and will always show you the past. But now it can show you images from several epochs of time in the past.