GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.
Qube Money - Qube Money is the #1 new budgeting app on a mission to digitize cash envelopes! Create a budget in minutes and start spending with purpose. Download the app today and start organizing your finances.
Ledger-cli.org - Ledger is a powerful, double-entry accounting system that is accessed from the UNIX command-line.
Mint - Free personal finance software to assist you to manage your money, financial planning, and budget planning tools. Achieve your financial goals with Mint.
Teamleader - CRM, invoicing & project planning in a single tool for SME's
Free Invoicing Software - Free Invoicing Software provides the facility of online billing.