Microsoft have announced that the External Collaboration Toolkit for SharePoint has been released and is now available on Microsoft TechNet at http://www.microsoft.com/collabkit. This accelerator helps you easily deploy a SharePoint-based external collaboration facility at your organization. Once this facility is in place, end users can quickly create a new collaboration site (using a SharePoint site collection) and add internal and external users to that site. Both these process can be workflow enabled so that an administrator must approve both site and user creation.
The toolkit runs on both MOSS 2007 and Windows SharePoint Services 3.0. It also leverages SQL Server 2005 and ADAM. All external users are created in the ADAM directory so they are segregated from your primary user store.