There's a nice series of images of Deimos (thanks to Pando for the positive ID) eclipsing the sun on Spirit Sol 420. You can use MMB to view a little movie of it.
More features are coming as soon as I can find enough time... One of the next things up will be the ability to open images in full size. Another thing that occurred to me tonight (watching the eclipse) would be a "reverse play" command-space key. There's lots more that could be done, but I don't want to get too far ahead of myself.