Microsoft has released a Solution Accelerator to quickly deploy sharepoint in an extranet solution.

From Microsoft's description:

This software and documentation helps administrators quickly deploy a SharePoint-based solution for collaborating across the Internet. The documentation includes Planning for External Collaboration with SharePoint, which describes the planning process for deploying the solution in a small or mid-sized environment, and the Deployment and Operations Guide, which explains how to install and configure the solution, provides guidance for users, and describes how to deploy the solution in larger environments.

External Collaboration Toolkit for SharePoint