We are setting up a new extranet farm and we want to use SharePoint 2010. We have some usability issues with authentication on our old farm, so I'd like to do things right (or at least righter) on this one.

Does SharePoint 2010 have an OOB way to support forms based authentication that will look in a trusted domain to validate an ID/password before searching a SQL datastore or is this something I'm going to have to write myself?

We are planning to set up alternative access mappings so that users within the office can use NTLM and SSO, but when outside the office, they'll access the site through SSL and we **want** them to be able to use the FBA form to enter their network credentials and get authorization.

Can anyone point me to a good resource or even a 3rd party provider that supports this already?