Integrating SharePoint Server 2007 with Community Server Membership Databases
Community Server is a great example of software that is built on top of the ASP.NET flexible membership services. The ASP.NET membership services enables their software to easily interoperate with other products that also use membership services, in this particular case SharePoint Server 2007.
I remember a while ago some folks in INDC talking about DNN vs SharePoint vs CS, and yesterday I found this article authored by Hans Hugli on MSDN. What a coincident!! I hope this link can be useful.