FusionInvoice!

GnuCash is personal and small-business financial-accounting software, freely licensed under the GNU GPL and available for GNU/Linux, BSD, Solaris, Mac OS X and Microsoft Windows.

InvoicePlane is a self-hosted open source application for managing your quotes, invoices, clients and payments. The application comes with various options, templates and settings to customize your invoicing experience.

HomeBank is a free software. Use it to manage your personal accounts. It is designed to easy to use. Analyse your finances in detail using powerful filtering tools and graphs.

BILLmanager is a linux-based control panel for automating client management, invoicing and billing. This software specifically developed for hosting service providers will help you manage and take complete control of various aspects of your business:

Send, track and collect payments quickly. Great for teams, freelancers and service providers. FreshBooks is an easy cloud accounting app for small businesses and freelancers, specifically designed to save you time billing clients. Create professional invoices, capture expenses with ease and effortlessly track time on projects; it’s all here, plus you’ll be ready for tax time.

FrontAccounting is a simple, but powerful, system for the entire ERP chain and covers:

The most popular version of Americas #1 small business financial software helps make your business more profitable.

Zoho Invoice is an easy invoice software meant for small businesses and freelancers. Accept payments online, automate payment reminders and recurring invoices easily.

Billomat Online Invoicing Tool is a perfect choise for every freelancer and small bussiness even for non-accountants. The Billomat service include customer management, quotes, invoices and reminders and what is most important its stress-free and secure!