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 RESTful Ei3 API is aimed at bringing its machine to machine communications to manufacturers looking to remotely control their machines, maximize efficiency, save energy, and cut back on green house gasses.