Fenwick & West have long been on the SharePoint bandwagon and Fenwick's Mark Gerow has litterally written the book on SharePoint on extranets for a law firm. In this article, he covers the technical issues and the human element of building and rolling out an extranet with SharePoint:
"In this article I'll discuss how Microsoft Windows SharePoint Services 3.0 (SharePoint) has been used at Fenwick & West to meet the challenge of making extranets available for each and every matter opened. I'll also cover the key issues that must be addressed in order to scale to thousands of extranets and terabytes of data. At the conclusion of this article you'll have a better idea of what can be accomplished with SharePoint at your firm, as well as a road map to get you started. "
This is a great article for anyone interested in SharePoint, especially those thinking of using it as an extranet.