The Netflix Prize offers a $1 million prize to anyone who can take anonymous ratings data from Netflix's database and build a recommendation system 10% better than their proprietary Cinematch system.
Netflix knows how customers rated certain movies. They withhold some of that data and ask that you come up with an algorithm that predicts how customers would have rated those movies based on their other ratings and the ratings of other customers. You submit your results, and if you can beat Cinematch's results on those withheld results, fame and fortune await, though you have to turn over your algorithm to Netflix but also share it with the world, which is interesting.
For each customer's movie rating, Netflix provides the date of the rating, the title of the movie, and the year of release.