This tutorial shows how to set up a CentOS 5.1 based 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 5.1, but should apply to the 64-bit version with very little modifications as well.
This is a useful site for information on centOS. From the main page click on Information, then FAQ, then CentOS general questions. There is a good list of typical questions asked about CentOS...enjoy!