Exclusive Content Password Protect is a plugin by Cliconomics that allows you to hide a section (or multiple sections) of content on your page or post. Use this to create exclusive content that you only want email or RSS subscribers to have access to. Once they enter in the global password once, they will have access to all content from then on. Plus you can use passwords for certain sections to have even more exclusive content.
Download andInfo: http://wordpress.org/extend/plugins/exclusive-content-password-protect/