An update from a recent query/summary posting on my math librarian mailing list (SLA/PAM):
http://en.wikipedia.org/wiki/College_and_university_rankings > has one of the best descriptions of various college /university ranking systems. They go through many of the different approaches including the controversies/weaknesses in methodology/reproducibility etc.
The April 2007 issue of the Institute for Higher Education Policy has an article titled, "College and University Ranking Systems – Global Perspectives and American Challenges”
Thanks to Marie C. Fraties-Block