Using CentOS 5.7, none of the default services are starting on boot. What would cause this?
Did they start before? Or, are they new applications that you've added since the initial install.
Were there any recent changes that you've made that may have caused the problem?
If they're new applications, you need to configure them with chkconfig to determine the runlevels (when they start). You can use the defaults as such:
So, for Apache:
If there is an issue on startup that is preventing the services from starting, check your syslog. You can do this via this command:
This displays any error messages that happen during startup. You might want to edit your initial question to add some additional details. Post the recent entries to the syslog that occurred after the last boot.