TurboCASH - TurboCASH Accounting Free and Open Source Accounting Software for Small to Medium Business.
Melissa Data Quality - Melissa helps companies to harness Big Data, legacy data, and people data (names, addresses, phone numbers, and emails).
GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.
CrankWheel - Insanely simple, enterprise-friendly screen sharing, free for individual use.
Xero - Xero is online accounting for your small business.
Denali (Cougar) - Denali (Cougar) is software develops leading on-premise accounting solutions for small to mid-sized businesses.