A (very) recent Nature paper suggests that Ceres has ammoniated phyllosilicates in the surface soil. (That is, nitrogen-bearing clay). The authors use infrared spectrum matching, a proven* technique.
(thanks to The Dragon's Tales for the link.)
This is a big deal. It means Ceres has abundant quantities of carbon, nitrogen, oxygen and hydrogen, much of it already in the form of organic molecules. We already know* it has a liquid water layer under the icy crust. It appears to be very similar to a CI chondrite, so there should be sufficient amounts of the other minerals required for plant life.
This makes Ceres a desirable destination for mining. With only 3% of Earth's gravity, moving huge amounts of material is fairly cheap. There is abundant water, carbon and nitrogen available and in easy to handle forms. It is the closest low-gravity body to Earth with proven water reserves and by far the closest such body with nitrogen reserves. (Most nitrogen we know of or predict is far enough from the sun to be nitrogen ice and far enough from Earth to take decades to retrieve.) Transit to and from Ceres is a long journey (2 years 7 months round-trip for short stay, 3 years 10 months for long stay), so this is likely to be an automated process. Still, this is going to be a much cheaper source of nitrogen (for breathing gas and fertilizer) than Mars or Earth if done properly.
This also makes Ceres a desirable destination for scientific exploration. There have been rumblings lately about a mission to Europa to look for life. Ceres has 22% of Europa's gravity, enough sunlight for solar power, a shorter travel time and only normal radiation levels (vs. Jupiter's hellstorm of invisible death). With launch windows every 1 year 3.3 months and travel times (via Hohmann transfer) of 1 year 3.5 months, science returns will occur rapidly. (Jupiter's one-way trip is about 2 years 9 months and launch windows are every 1 year 1 month, so a Ceres mission is 16 to 18 months shorter.) The delta-V to Ceres is about 9.5km/s to orbit and 0.3km/s to land while Europa is about 25.2km/s to orbit and 1.4km/s to land. Equipment meant for exploring the outer icy moons could be tested at Ceres under less hazardous conditions and for less money. For the cost of one Europa mission we could send about five similar payloads to Ceres for competitive testing, not to mention the science return and the add-on opportunities to observe other bodies in the asteroid belt (perhaps including one or more permanent telescopes in orbit around Ceres).
* The word "know" represents more of a sliding scale. Until we have actual samples of these compounds taken directly from Ceres we will not know for sure. Until we drill a shaft and see actual liquid water, again, we cannot be 100% certain. Still, given the evidence at hand these conclusions appear to be sound and sufficient reason for a Ceres lander to collect this evidence.