Saturn's two largest moons, Rhea and Titan, line up for the Cassini orbiter. Rhea's pock-marked surface provides a beautiful contrast to the golden glow of Titan, even though they're both actually made up of largely similar material.
The little grey ball is Dione, the third largest of Saturn's moons. The large brown sphere with the ethereal haze is Titan, the largest. In the background, that's Saturn and its rings. Never has an astronomy picture looked so painterly to me.