Hide Admin Panel from Subscribers Plugin for WordPress
This plugin prevents subscribers from viewing the WordPress admin panel located at /wp-admin/. They are instead shown a custom message that you specify, as well as an optional logout link. You can use HTML tags and CSS in your message to style it any way you choose. Logged in users who have more access than subscribers are shown the standard admin panel.
http://www.dagondesign.com/articles/hide-admin-panel-from-subscribers-plugin-for-wordpress/
