At the risk of alienating the entire audience by posting about licensing, I want to provide the answer to a question I get asked frequently by ISVs.
While lots of ISVs find the features of MOSS cool and compelling, they typically raise concerns about how to license it for sites that have some sort of public facing aspect (Internet and/or Extranet.) After my standard response of "try the partner helpdesk" grew tiresome, I decided to do a little research into the topic by asking my team members if they had a better answer. It turns out that Jason De Lorme had already gone through much of the pain in tracking this down, and was kind enough to share the following.
If you're planning on building a MOSS site for Internet (like http://www.microsoft.com) or Extranet scenarios (like http://partners.microsoft.com), the Microsoft Office SharePoint Server for Internet Sites licensing model quite likely applies. In this model, there's no need for individual clients to have CALs when accessing your site - a great advantage for anyone considering using MOSS in this way.
So have no fear - you can build afforable public MOSS sites!