Invoice Ninja - Invoice Ninja is a free, open-source solution for invoicing and billing customers.
FreshBooks - The ideal accounting software for small business owners.
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
Sage 50cloud - Sage 50cloud is the small business solution for everyday heroes. Plus, new customers enjoy 40% off!
GnuCash - A personal and small-business financial-accounting software, licensed under GNU/GPL and available for Linux, Windows, Mac OS X, BSD, and Solaris.
LessAccounting - Small business accounting software from Less Everything, because your job title isn't accountant! Accounting software features: invoicing, proposals, CRM and more.