GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.
DataNote ERP - DataNote ERP is a complete ERP solution built for multiple industries such as construction, engineering, food and beverages, metal processing, and healthcare, among others.
Synder - AR Automation
PracticePanther - PracticePanther offers CRM, invoicing, time tracking and communication solutions for law firms.
Xero - Xero is online accounting for your small business.
iDempiere - iDempiere Business Suite ERP/CRM/SCM done the community way.