Professor Kumar has also done a more detailed treatment of K-Means clustering, slides are available here.
Browse the ACM Communications Special Issue on Data Mining: Communications of the ACM 39(11), November 1996. Pay particular attention to the article by Usama Fayyad, Gregory Piatetsky-Shapiro and Padhraic Smyth, ``The KDD process for extracting useful knowledge from volumes of data'', pp. 24-26.
Let me know if you have trouble getting the article - I thought we were site-licensed for the ACM digital library, but access seems to require a password. If you are an ACM member, your standard ACM account/password will allow you access to Communications.
I couldn't find a good article on Self-Organizing Maps available on-line. There is a reasonable treatment available as part of Samuel Kaski's thesis - he was a student of Professor Kohonen.