marcucci

This is a very simple plugin that will check to see if a visitor is logged in before allowed your WordPress site to be displayed. 
If they are not it will display the login page of your site. It will also add text on the login page to explain that the site 
required all visitors to login.

Password Protect Plugin for WordPress

Force all visitors to login before accessing your wordpress site and add a message on the login screen explaining that login is required.

Josh Hartman

Tired of untagged posts? Use this simple plugin to require users to add at least one post tag before saving a draft, updating a post, or publishing a post. This applies to normal posts and may not be compatible with custom write panels or custom post types.

Require Post Tags

Require users to add at least one post tag before saving a draft, updating a post, or publishing a post.  This applies to normal posts and may not be  …

Password Protect Plugin for WordPress vs Require Post Tags