A good place to look is Carnegie Mellon University's http://lib.stat.cmu.edu/DASL/Data and Story Library or DASL, which contains data files that "illustrate the use of basic statistics methods... A good example can make a lesson on a particular statistics method vivid and relevant. DASL is designed to help teachers locate and identify datafiles for teaching. We hope that DASL will also serve as an archive for datasets from the statistics literature."