I've done this on my site using PHP. Being a member of the site allows my members to do lots of things like rate pictures, links and write reviews. They can also sign-up to a newswire service. If they're not logged in (no UBB cookie set) most of the pages remind them to login. This is a simple PHP page that asks them for their login details before comparing them to the UBB files to make sure they're accurate. If it works, I create the UBB cookie with PHP so it works on the forums when or if they move to that area of the site.
It works really well and the UBBmemberID is written to the MySQL tables when they rate or write a review and a check is made the next time they come around and says "sorry, you've already rated this picture" etc.
The newswire page just collects UBBmemderIDs and puts them in a MySQL table. When I send out an email it then reads through the MySQL table, extracts the current email address from the UBB Member file and sends the email to them.
It means the UBB member database is used across the site and the UBB blends in with everything else.
