Apache comes preinstalled on all Macs running OS X and OS X server (certainly Tiger and Leopard, I don't know about the earlier versions as I have forgotten but chances are it was on them as well).
Any Apache tutorial will do. Just be aware that the configuration files are stored in /etc/apache2 rather than where they are normally stored on a Linux box. So just change the paths appropriately and you are golden.
It is also worth noting that running a web server on a home computer is pointless unless it is just for internal use. You won't have the bandwidth available to run a proper website on your computer.