Invoice Ninja - Invoice Ninja is a free, open-source solution for invoicing and billing customers.
Mint - Free personal finance software to assist you to manage your money, financial planning, and budget planning tools. Achieve your financial goals with Mint.
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
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.
GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.
Ledger-cli.org - Ledger is a powerful, double-entry accounting system that is accessed from the UNIX command-line.