Left image: Earth as seen from Mars looking north-west in the twilight of February 12, 2012, shortly after Sunset, as visualised in Stellarium. The location is approximately the same latitude on Mars as Adelaide is on Earth. The right image is what Earth would look like through a telescope. Click on any image to embiggen. An earlier version from November 2011 is here.
The evening sky on Mars is quite lovely at the moment, with Earth, Venus and bright Jupiter all lined up. Earth will disappear from view very soon as Mars moves into opposition (where the earth is directly between Mars and the Sun. From our point of view, Mars will be at it biggest and brightest and visible all night long).
Once again one of the top search terms for people visiting my blog, is "Earth from Mars", probably in response to more publicity about the "John Carter on Mars" movie. So, once more, here it is for you searchers.