fergbrain

Forces new users to register additional fields. Available fields are:
<ul>
<li>First Name</li>
<li>Last Name</li>
<li>Nickname</li>
<li>AIM screen name</li>
<li>Yahoo IM screen name</li>
<li>Jabber/Google Talk user name</li>
</ul>

Force User Field Registration

Forces new users to register additional fields (such as first name and last name). Note: WordPress 2.5 or higher is definite required due to new erro …

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.

Force User Field Registration vs Password Protect Plugin for WordPress