One idea is to set a password for every post you want to keep private but leaving the front page without password.
(If you already have lots of posts, the above solution can be really tedious. You also might want to change the password regularly…)
It’s easier to bulk edit and set all the posts to Private, not Password-protected. I did that with a blog: http://lolebrity.wordpress.com and it’s much simpler. Go to Edit Posts and you can tick off “Set to Private” for all the posts on that page. So it means you can edit 20 at a time.