I had an academic appreciation that it is complicated to send a rover like Spirit to Mars, but until watching this animation I didn't appreciate how complicated. What a terrific project! It makes me proud, once again, to be an American. (And also to be an alumnus of Caltech, whose Jet Propulsion Laboratory is responsible for NASA's unmanned missions.)
This animation is fabulous and awe-inspiring. By all means check it out! [ via Joi Ito ]
Also, you might want to visit the JPL website, they have a ton of great Mars pictures, animations, and discussions...