MSDN Technical Articles
Microsoft MSDN has a three-part technical series on Forms Based Authentication on MOSS and WSS. Introduction (Part 1) Forms Authentication Samples (Part 2) Differences Between Forms Authentication and Windows Authentication (Part 3)...

How do I take a custom action upon SharePoint FBA user login?
How to take a specific custom action when an FBA (forms based authentication) user logs in....

Configuring Multiple Authentication Providers for SharePoint 2007
Talks about the topic of configuring multiple authentication providers for SharePoint 2007....

geekSpeak Recording: Custom Authentication Providers for SharePoint Server 2007 with Ron Rohlfs
Ron shows how to have some users authenticated against Active Directory while some users are authenticated against a custom provider....

ASP.Net Providers for SharePoint Developers
Demonstrates how to create and install your own provider for SharePoint 2007....

HOWTO: Configuring a Office SharePoint Server 2007 Publishing Site with Dual Authentication Providers and Anonymous Access
HOWTO: Configuring a Office SharePoint Server 2007 Publishing Site with Dual Authentication Providers and Anonymous Access...