Invoice Ninja - Invoice Ninja is a free, open-source solution for invoicing and billing customers.
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
FreshBooks - The ideal accounting software for small business owners.
GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.
Expensify - Import expenses directly from a credit card to create free expense reports quickly. Approve reports online and reimburse directly to a checking account with one click.
TimeStatement - A simple time & expense tracking software with powerful invoice & report generation, best Excel alternative / extension, timesheet...