Picture from Viking1
Though regarded by many at the time as uninspiring, these images provided a great foundation upon which the the two Mars Rovers - Spirit and Opportunity - have soared. NASA has done an amazing job with both rovers. In fact, they didn't think they would still be around seven years later. Check out NASA's great webpage with updated info, and awesome pictures - both color and black & white.
Mars is truly fascinating. I wish I could go to explore every inch of its landscape. I guess I'll just keep living through those who know way more about it than I do.