Xero - Xero is online accounting for your small business.
SendRecurring - SendRecurring allows you to setup, send, and maintain scheduled email reminders.
Datamolino - Process all invoices without retyping. We turn your invoices into structured electronic documents, that you can import directly into your accounting system.
Recurrr - Send recurring emails
DOKKA.com - The Future has Arrived: Accounting Process Automation
FollowUpThen - The simplest way to schedule an email reminder