A Kerberos primer
http://www-106.ibm.com/developerworks/library/it-kerbero.html?dwzone=ibm
The Moron's Guide to Kerberos
http://www.isi.edu/~brian/security/kerberos.html
Kerberos Primer: Understanding Kerberos
http://www.stanford.edu/services/kerberos/userguide/primer.html