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.
Odoo (formerly OpenERP) is a suite of open-source business apps written in Python and distributed under the AGPL license, under the Open Core software business model. It is used by 2 million users worldwide to manage companies of all size.
ERPNext is a free and open-source integrated Enterprise Resource Planning (ERP) software developed by Frappé Technologies Pvt. Ltd. and is built on MariaDB database system using a Python based server-side framework.
Dolibarr ERP & CRM is a modern and easy to use open-source web software package to manage your business (customers, invoices, orders, products, stocks, agenda, e-mailings, shipments...).
From invoicing to expense tracking to accounting, Akaunting has all the tools you need to manage your money online, for free.
Ledger is a powerful, double-entry accounting system that is accessed from the UNIX command-line. This may put off some users, since there is no flashy UI, but for those who want unparalleled reporting access to their data there are few alternatives.
inoERP is an open source php based enterprise management system. The ERP systems contain all the required modules for running any small to mid-size businesses. The features are very similar to Oracle R12/ Fusion Application and SAP. It also contains a light weight CMS which sea.
Manager is free accounting software for Windows, Mac and Linux.
It features an intuitive and innovative user interface with modules such as cashbook, invoicing, receivables, payables, taxes and comprehensive financial reports.
The desktop edition is free while the cloud edition.
Free and open source human resource management software (HRMS / HRIS) with rich features and easy to use interface. It covers personnel information management, employee self service, leave, time & attendance, benefits, and recruitment.
Tryton is a three-tiers high-level general purpose application platform under the license GPL-3 written in Python and uses PostgreSQL as database engine. It's the core base of a business solution providing modularity, scalability and security.