The UCI Repository Of Machine Learning Databases and Domain Theories - ftp://ftp.ics.uci.edu/pub/machine-learning-databases

UCI Repository Of Machine Learning Databases and Domain Theories contains data sets and domain theories that have been or can be used to evaluate learning algorithms.
There is a README file listing the datasets, but this is dated 4th December 1995.

Note: This info converted from the original "The Data Mine" pages and pre-dates June 2001. Please remove this note if you update or check the info