MailCampaign is a bulk e-mail system that we wrote ourselves, as our customers needed a simple way of sending newsletters.
MailCampaign supports multiple lists, instant unsubscribe and rich-text e-mails. There is a easy-to-use wizard that takes you through setting up a campaign to sending it.
MailCampaign can also be used as a data capturer, letting users fill in custom-built forms that you can create easily though a simple drag-and-drop interface.
The system works on a pre-paid basis, and you only pay for messages you send, at very affordable rates.