Invoice Ninja - Invoice Ninja is a free, open-source solution for invoicing and billing customers.
Payable - Easily manage and pay your contractors
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
OpenSourceBilling - OpenSourceBilling (OSB) is a super simple way to create and send invoices and receive payments...
GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.
Stilt - Free US bank account and card for Immigrants