The UCI machine learning repository [1] contains a wealth of data sets intended to be used for machine learning. Many of the data sets have had analyses performed on them that could be considered canonical. For example, the Abalone dataset's [2] associated problem is the prediction of a specimen's age, given its measurements. The problem has been analysed thoroughly; a cursory Google search for "Abalone data set" reveals that plenty of people have considered the problem.
Also Amazon (via AWS) [3] have made it really easy to access public data sets.
I hope this is helpful.
[1] http://archive.ics.uci.edu/ml/