Sendy - Sendy is a self hosted newsletter app that sends emails 100x cheaper via Amazon SES
Mailman - Mailman is free software for managing electronic mail discussion and e-newsletter lists.
Listeron - An email address for your group. Discuss. Debate. Organise. All with email.
SendPulse - Maximizing e-mail marketing open rates automatically
WP Mailster - WP Mailster enables you to run a listserv-like email discussion list on your WordPress site.
mlmmj - Mlmmj is a simple and slim mailing list manager (MLM) inspired by ezmlm.