Power List is a great mailing list manager for any site, large or small. Power List works by users entering their email address in a form with then writes it to a storage text file. When you want to send email to all the addresses in your list, you goto the mail.cgi file where you enter your message in the from provided, enter your password and then submit and email is sent to all.
Users can also delete their address from the list when ever they feel like it.
The basic advantages of this script is that at subscribe or unsubscribe, the user remains on the same page on which there was registration. He does not leave the registration page and sees only JavaScript confirmation message. Mail Machine is a great mailing list script that allows visitors to your website to subscribe and unsubscribe to your mailing list without any work from you. This is a great way to inform your visitors on what's happening, and bring them back. Easy to setup and customise.