WordPress Info And Tips

The Subscribers-Only plugin lets you mark posts for subscribers-only. No template modifications are required.

You define which roles are allowed to read subscriber-only posts.

In order to read posts marked for subscribers-only a person much register at your site and login.

When a post is marked as "subscriber-only" and your home page displays excerpts then the excerpt will be shown along with an optional "Subscribers-only" banner that you define. When a reader clicks on the link to go to the individual post page they must be logged in to read the post. If a person is not logged in then they will be presented a link to login or register.

If your home page doesn't display excerpts then no post body content will be displayed for a post marked as "subscribers-only". Instead the reader will see a link to login or register.

If a person is already logged in, but their role isn't allowed to read a subscribers-only article then they will be presented with a "notice" message (if you define one) that informs them of their current membership level along with additional text that explains that they cannot read the post. A link can be provided to either register or login — assuming that they might want to register another account or login with another already-existing account.

Read more and get a copy here:
http://edwards.org/2006/03/07/subscribers-only-plugin-for-wordpress/