If the Earth and Moon weren’t enough, Google is using its map technology to provide images of Mars. Currently available is a false color elevation map, a visible map (which is in black & white), and a high-detail infrared view.
There are also markers for Mars landers (such as Spirit & Opportunity, as well as the planned landing sites of failed missions), geographic features, and named regions.

Google has registered domains for GoogleMercury, GoogleVenus and GoogleJupiter, but says it has no current plans to provide other planets at this time.