ChargeOver - ChargeOver automates recurring billing, subscription billing, & payment acceptance. A SaaS that integrates with Xero, Quickbooks, & has an API. Free trial.
VOGSY - Professional service automation tool built on Google G Suite
Elorus - A super-easy online invoicing & time tracking software
Timewatch - Timewatch offers time tracking, expense management, resource scheduling and professional services automation solutions.
MinuteDock - Web-based time tracking software designed to integrate with the Xero accounting package.
Krow - Krow Software is a professional service automation solution.