Alternate Access mapping is a new technique used in SharePoint 3 for handling url:s when you access sharepoint from different environments, for instance, maybe you both want to be able to access your sharepoint internaly using http://sharepoint and externally using https://sharepoint.humandata.se, well, by using a good firewall the redirection is possible but the problem arises when you want searching and other url:s to work properly.
To be able to handle this properly, a function called Alternate Access Mapping is used. The SharePoint Technology Team blog discusses it further and describes how to set it up.
Since this is quite a normal setup, and there are certain aspects of this that are a bit complicated, like only having to log on once, we at Humandata are working on a best-practice for how to set this up properly that is based on the Microsoft best-practice. When we're done, I'll let you know.
CRM and SharePoint Consultant