Hosting multiple websites is easy to do with the built in Server Admin utility within OS X Server. You can point your DNS for multiple domains to the same IP and Apache (Web Server) will respond with a different virtual host document root depending on the hostname requested. Add aliases to allow Apache to respond to the “www.” requests as well as any additional domains for the virtual host “.net, .org, etc”.
Note: This applies to Server Admin in OS X 10.6 Snow Leopard, not for OS X 10.7 or newer.