Today's Image of Mars shows the Tharsis Trio (Arsia, Pavonis, and Ascraeus Mons) and Olympus Mons off to the Northwest. This image is very similar to one previously showcased by Mars Travel from the European Space Agency's Mars Express.
The Tharsis Trio are aligned in almost a perfect line pointing Northeast. Scientists speculate that all these volcanoes formed from a larger fracture/vent system that caused the three initial eruptions that created the Tharsis Trio. In other images you can see the vents pointing Northeast from Arsia Mons toward Pavonis and Ascraeus Mons, which lend credence to this theory.
As far as I can tell this image was taken by Mars Odyssey Orbiter's THEMIS (please correct me if I'm wrong) Click on this image to see the original high resolution image.