Comment Approved Notifier sends an e-mail to your commenters when you approve their comments. It is a very simple plugin. There are no settings, options. It starts to work when you activate it.
Read Please
If you upgraded to WP 2.7 or WP 2.8, please, update v1.1 to v2.1 It requires at least 2.7. If you use WP 2.6.5, please use version 1.1
Thanks!
This plugin is available for download for your site.