PHPList is a simple and free script for building mailing lists. you can find it at http://www.phplist.com/ I would warn you though, if you plan on using it to send out emails, it would be a good idea to host it on a different server than you usually use for email. When we used the program in the past we found that a lot of mail servers started blocking us just because we were using the program.

We currently use a 3rd party to send out emails, the company is call gotmarketing.

Hope this helps.