In a website, I need to integrate membership and authentication. So I want to use the functionality of ASP.NET Membership, but I have other custom stuff, that a \"user\" has
I ended up writing my own membership-provider, and have implemented that in 3 separate solutions now. It is extremely simple and much, much more elegant than linking a user to a membershipUser (which I have also tried).
Read this...:
Create Custom Membership Provider for ASP.NET Website Security
And if you want to learn more, watch this video (with sourcecode).