ChargeOver - ChargeOver automates recurring billing, subscription billing, & payment acceptance. A SaaS that integrates with Xero, Quickbooks, & has an API. Free trial.
MinuteDock - Web-based time tracking software designed to integrate with the Xero accounting package.
Elorus - A super-easy online invoicing & time tracking software
fusebill - Fusebill is the leading recurring billing and subscription management software for businesses. Try Fusebill for subscription billing made easy!
Street Invoice - Mobile Invoicing for Android, Blackberry and Windows PC
INVO - Online invoicing & warehousing tool with native Android app