While most people think of Mac OS X as a client system only, you can also run Mac OS X as a server. If you need Apple's advanced administration tools, you could purchase and use Mac OS X Server (http://www.apple.com/server/macosx), but if you're comfortable with the command line, the client version can be coerced a bit to run as a server.
The services that power the Sharing preference panel are based on the same servers that power much of the Internet:
However, the System Preferences are limited in what they will let you do. To unleash the full power of Mac OS X as a server, you'll need to install your own administrative tools or edit the configuration files by hand.