[CentOS] Disabling services in CentOS 5.5

The following NSA document provides very good information on the secure 
configuration of Red Hat Enterprise Linux 5/CentOS 5.x:

Guide to the Secure Configuration of Red Hat Enterprise Linux 5
http://www.nsa.gov/ia/_files/os/redhat/rhel5-guide-i731.pdf

It goes through almost all the services and gives you guidance on 
whether and how you should disable a service.