Well, you could purchase a copy of Mac OS X Server which has the nice graphical consoles for stuff like Apache, e-mail, and any other services that you want to serve out. You could also use a stock Mac OS X client installation, but that would require rolling up your sleeves and configuring some config files manually in order to override the default configs for client operating systems. For the record, Mac OS X (both versions) come with Apache, SSH, FTP, and other file and remote services already installed.
You could also install a non-Apple operating system like Linux/ppc or another open source Unix, but that would also require you to manually configure files for stuff like Apache and other services. However, the beauty of open source is that there are web consoles like Webmin and Swat and some others for configuring such files with an easy-to-understand web interface. And these operating systems and server applications and service front-ends are all available for free. Still, they're nothing like the console tools that come with Mac OS X Server.