It hasn't been officially announced yet, but as reported by this blog post, Google has launched a new service: Google Mars
It's just like Google Maps, except that it allows you to view Mars (doh!). There are three different views: Elevation, Visible, and Infrared. There are also clickable landmarks for the various successful and unsuccessful Mars spacecraft, lists of named regions and craters, and more.
Check it out, it's pretty cool!