*(updated on 5/30/2014) For those interested, I have released an Extranet Module to manage creating and removing an extranet for your site.
I've recently needed to setup an extranet for several websites and began researching. There are several helpful articles on the topic. I found bolaky.net and blog.wojciech.org as well as using Sitecore's Security API and Security Administrator cookbooks. Although there was enough information to get me started, what I found was disjointed and there were a few specifics that weren't detailed. After some testing I was able to create a functioning extranet and in an effort to create a more comprehensive article I have detailed my results.