Light from distant galaxies shining through foreground galaxies offers an approach to measuring dust properties which is complementary to IR emission. Its utility was long limited by the very limited number of suitable galaxy pairs (such as NGC 3314) identified in the local Universe. Even so, they furnished valuable information on consistency of dust masses from emission and absorption, the slope of the reddening law in other spirals, and the radial attenuation profiles. However, over 2000 such overlapping galaxy pairs were identified as a spinoff of the Galaxy Zoo project, enabling a host of new applications. Followup studies, many still in progress, have measured the effective attenuation curve of spiral disks in the UV, shown how resonance rings can clear their radial neighborhoods of ISM, found rare dust lanes at large distances, and begun to probe radial attenuation profiles and their diversity. An ongoing HST snapshot program, STARSMOG, is improving the sample of dust lanes and disk locations probed in this way, while a new sample of overlapping pairs from Hubble Zoo offers the possibility of using a single technique to probe the cosmic evolution of dust attenuation.