I wouldn't be a very good space nerd if I didn't post about this. There is now an overlay to "Google Earth" where you can check Mars out, with lots of the imagery from the spacecraft we've sent there superimposed. It's nothing short of awesome. Check out the news article.
Several years back, right after Google Earth was first released, I emailed the good folks at Google and suggested that they do this very thing. I don't know if I was just one of a million people who made that suggestion, and they never even emailed me back, but it's good to see it finally come to fruition. They also include specific images from the NASA archives, with links to descriptions of the different things to be seen. It's awesome.