Microsoft published a new guide: Publishing a SharePoint Site Accessible to External Users
Many organizations require an efficient way to share files, folders, and resources and easily collaborate on the same document with people outside of the network. Using the Windows SharePoint Services solution in Windows Small Business Server 2003, organizations can now easily collaborate with users outside of the local network to satisfy this business need. This document does not include information about publishing a SharePoint site accessible to external users using Microsoft Internet Security and Acceleration (ISA) Server.Publishing a SharePoint Site Accessible to External Users 1.0
