I haven't thought about the Open-Source Sky Survey in a long time, but my NIPS submission with Lang and Schölkopf made me think about it again. We can combine all the images of the night sky ever taken into an all-sky map with an algorithm that is robust to calibration and transformation problems and that is linear in the total data size. That's awesome! Now I just hope we maintain momentum after the (unhealthy, insane) NIPS deadline.
[ps. This post violates the anonymity requirements of NIPS. That just shows that submitting to NIPS is not consistent with my ideals of open science.]