Howtoforge published a guide about setting up CentOS 5.0

This tutorial shows how to set up a CentOS 5.0 server that offers all services needed by ISPs and web hosters: Apache web server (SSL-capable), Postfix mail server with SMTP-AUTH and TLS, BIND DNS server, Proftpd FTP server, MySQL server, Dovecot POP3/IMAP, Quota, Firewall, etc. This tutorial is written for the 32-bit version of CentOS 5.0, but should apply to the 64-bit version with very little modifications as well.

The Perfect Setup - CentOS 5.0 (32-bit)