For those who work with SharePoint Portal Server 2003 on a regular basis, you may be interested in this short tutorial on how to create a web site in IIS and the alias that web site in DNS:
http://www.smallbizserver.net/Default.aspx?tabid=170
The one difference between this article and how we do it in SharePoint is that we don't assign an IP address to the SharePoint virtual server. Instead, we leave the IP address at All Unassigned, and use host headers to differentiate between multiple web sites.
But that is where DNS comes in. DNS aliases help us use multiple names to refer to the same server but to different web sites on that same server.
This article is nicely done.