When I'm deciding which intergalactic data set to work with, I don't want to take any half measures. That's why I'm drawn to the Sloan Digital Sky Survey (SDSS). In their own words, "The Sloan Digital Sky Survey (SDSS) is one of the most ambitious and influential surveys in the history of astronomy." Sounds like their putting the project right up there with the greats like Galileo. You can bring this level of astronomical greatness into your app via the SDSS APIs: SDSS cone search & SDSS image cut-out.
The Gray Lady is getting her code on. In Andre Behrens's New York Times blog, Open, billed as "All the code that's fit to printf()," he recounts events on coding and science held in 2012. Two of the notable events were the well-attended one on Big Data and Smarter Scaling and their Open Source Science Fair.