FreshBooks - The ideal accounting software for small business owners.
BillGrid.com - BillGrid is an easy to use online invoicing, billing and expense management system that will save you time with tracking clients projects, expenses, invoices and payments.
QuickBooks - Business runs better with QuickBooks, the #1 accounting solution for small business.
ChargeOver - ChargeOver automates recurring billing, subscription billing, & payment acceptance. A SaaS that integrates with Xero, Quickbooks, & has an API. Free trial.
Akaunting - Free, open source and online accounting software for small businesses and freelancers
MinuteDock - Web-based time tracking software designed to integrate with the Xero accounting package.