2 Blogs, 1 hidden

Anyone know how I would go about installing 2 blogs on 1 site, while keeping one completely password protected? I want to have my “professional” posts 100% public, but keep a personal journal separate that only my friends will have user name/passworded access to. I’d like to put the link to that part of my website on the navigation bar with a user login page. Anyone know how to do this?