The Sloan Digital Sky Survey (SDSS) is a fascinating attempt to map the entire sky at unprecedented levels of details, using digital cameras on large telescopes.  The data collected in the various projects making up SDSS are of enormous value to astronomers, as they can be mined for experimental data, or used as a reference to compare against recent images.  Probably the most well known user of SDSS data is Zooniverse, who gave us the citizen science project Galaxy Zoo.

The third survey (SDSS-III) was recently completed, consisting of four surveys executed on the same 2.5m telescope: the Apache Point Observatory Galactic Evolution Experiment (APOGEE) the Baryon Oscillation Spectroscopic Survey (BOSS), the Multi-Object APO Radial Velocity Exoplanet Large-area Survey (MARVELS), and the Sloan Extension for Galactic Understanding and Exploration 2 ( SEGUE-2).

And the best part?  In the grand tradition of astronomical research, all their data is made available online, for other scientists and the general public to freely browse and study.  At no cost!  I think some of the other sciences could learn a thing or two…