Invoice Ninja - Invoice Ninja is a free, open-source solution for invoicing and billing customers.
Composity ERP - Composity ERP is an integrated cloud-based enterprise resource management software to process sales, operations, financial performance and optimize inventory.
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
Odoo - An all-integrated business app suite to unleash your growth potential.
GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.
ERPNext - The ERP Software that helps you take full control of your business. ERPNext is both powerful and easy to use.