Million Song Dataset .... dodn´t really see context
movielens and grouplens datasets
The closest is the moviepilot dataset... which is no longer available
http://2012.recsyschallenge.com/tracks/camra/ ...
Building a dataset is a project in itself but in the last two years or so there has been a effort to provide academics with datasets so the recommendation system area can move more towards real-world applications
none the less there is much work to be done...
if you find anything please let me know :) i´m currently trying to find a similar dataset ... specifically something on music