Andrew Carol Wired Science Wired.com
The Antikythera mechanism, ca. 2nd c. BCE, is a bunch of gears and doodads which are thought to have been used to compute eclipses. Now one Andrew Carol has replicated the thing in Legos (not, as I usually say, "Lego blocks," because there are a lot of non-block-like pieces involved in this). There is a short (2.5-minute) video showing how he built it and how it works. Lots of cool math, involving the fraction 5/19. Underneath the article, there are several links to other pages about the original and the replica.