Forms Based Authentication in SharePoint: Web Administration Tool
One of the big new things (among tons of others of course) in SharePoint 2007 (both WSS v3 and MOSS 2007) is the fact that SharePoint now uses the authentication provider model of ASP.NET 2.0. This means that you have store the user accounts and passwords in another data source than Active Directory (the only option in SharePoint 2003), for example a SQL Server database. The good news is that SharePoint is relying on ASP.NET 2.0 for this, so if you know how to enable Forms Based Authentication in ASP.NET 2.0 sites, you also know how to enable it in SharePoint 2007! Enabling it is one thing, adding users to the database that stores the user accounts is another thing. Techies probably know lots of ways to create user accounts: stored procedures, sql statements, Visual Studio's Administration Site, ... But out-of-the-box there is no UI available to actually do that in ASP.NET 2.0/SharePoint 2007.
Luckily there is the fantastic SharePoint community: Chandima has just released his Forms Based User Administration Feature. I haven't tried it, but it seems the very nicely implemented: it uses features for deployment, web parts for the UI and even a CAPTCHA is present! Very slick! Now the road to create self-registering SharePoint sites is wide open! Get it from CodePlex.