Security WordPress Plugins
Free
Email Address Encoder
Automatically encode every email address in your posts and pages to protect it from spammers and attackers. Uses decimal and hexadecimal entities so there's no Javascript or extra code.
Free
Password Protected
Hide your entire WordPress site behind password protection. Any users visiting your site will be greeted by a login page which prompts them for a password that you specify.
Freemium
Better WP Security
Gives you a list of security tweaks that you can make for your website in a variety of different categories. Also performs regular database backups in case the worst happens and you need to restore everything.