With WSS V3 and MOSS 2007 you can leverage ASP.Net pluggable authentication modules. Thus providing the ability for a WSS site to leverage user authentication via a datastore other than Active Directory or Windows based logins.
This project provides WSS site's with a Feature set that will enable adiministrators to manage users of a data store with Forms authentication.

​​http://www.codeplex.com/MOSSFormsFeature​​

​​http://blogs.microsoft.co.il/blogs/bursteg/archive...​​