GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.
Composity ERP - Composity ERP is an integrated cloud-based enterprise resource management software to process sales, operations, financial performance and optimize inventory.
Xero - Xero is online accounting for your small business.
Odoo - An all-integrated business app suite to unleash your growth potential.
CheckStream - CheckStream check printing software
ERPNext - The ERP Software that helps you take full control of your business. ERPNext is both powerful and easy to use.