ChargeOver - ChargeOver automates recurring billing, subscription billing, & payment acceptance. A SaaS that integrates with Xero, Quickbooks, & has an API. Free trial.
Simple Invoices - Never Wait For Clients To Pay You Again!
MinuteDock - Web-based time tracking software designed to integrate with the Xero accounting package.
Express Invoice - Express Invoice is the easiest system for creating and tracking quotes, orders and invoices for your business. Use web access to view your data from anywhere.
Elorus - A super-easy online invoicing & time tracking software
FreshBooks - The ideal accounting software for small business owners.