This plugin provides a comprehensive subscription management system for WordPress blogs. It provides two levels of subscription:
Registered Subscribers
Public Subscribers
Registered Subscribers are users who have registered with the blog. They can login to manage their own subscription choosing plain text or HTML email format and selecting to receive notifcations when posts are made in specific categories. There is also an option to receive an excerpt of the post or the full post if plain test is selected.
Public Subscribers can subscribe and unsubscribe through a convenient web-based form. All requests require confirmation by email. Public subscribers have no choice about the type of subscription.
Administators have several management functions including configuration of the email templates used for new post notifications and (un)subscription requests. Administrators can also subscribe or unsubscribe users, as well as send out an email to all confirmed subscribers.
The format of the email can also be customised for per-post notifications, subscribe2 can generate emails for each of the following formats:
plaintext excerpt
plaintext full post (Registered Users only)
HTML full post (Registered Users only)
More Info:
Plugins
There is also a paid for version – Subscribe2 HTML provides all of the features of Subscribe2 with the addition of:
Sends HTML emails sent to all confirmed public subscribers
Has the ability to send HTML emails from Post->Mail Subscribers
Sends Digest Emails containing HTML.
More Info:
http://wpplugins.com/plugin/46/subscribe2-html