On registered approved members can view site.

I would like to have my home page be a login/registration page.  No content shown at all.  Once the user registers and is approved, then they would have access to the site.  Are there instructions or modifications anywhere that will explain how to do something like this?

Sure, every block and every menu item can be set for members only or for public viewing.  Just set everything to members only.  As for putting your registration on the homepage, there was a discussion on this a while back - someone did a mod for this - maybe mrpowless - check out his blog.