Openbravo

http://www.openbravo.com/
Openbravo is a fully functional integrated web-based open source enterprise management system (commonly known as ERP) that is much more at a cost that is far less: be the true owner of your ERP and only pay for the professional support that you really need. The solution is designed for small and mid-sized companies (SMEs) that are looking for an integrated way to manage their operations, optimize processes, increase customer satisfaction and ultimately increase profitability. Since 2001, Openbravo is used by many companies of varying size and across a wide variety of business sectors, from distributors to service and industrial companies

SugarCRM
http://www.sugarforge.org/
Sugar CRM is the world's leading provider of commercial open source customer relationship management (CRM) software. Founded as an open source project in 2004, SugarCRM applications have been downloaded over five million times and currently serve over 500,000 users in 75 languages. Over 4,000 customers have chosen SugarCRM's On-Site and Cloud Computing services over lock-in based, proprietary alternatives. In the last year, SugarCRM has been recognized for its customer success and product innovation by CRM Magazine, InfoWorld, Customer Interaction Solutions and Intelligent Enterprise.

Magento
www.magentocommerce.com
Magento is groundbreaking eCommerce software. With more than 500,000 downloads – and counting – it is the fastest growing eCommerce platform in the market. A feature-rich, enterprise-grade eCommerce solution, Magento offers merchants complete flexibility and control over the user experience, content and functionality of their online stores. Magento’s intuitive administration interface includes powerful tools for marketing, search engine optimization and catalog management, enabling merchants to create sites tailored to their unique business needs. Designed to be completely scalable and backed by an extensive support network, Magento offers companies the ultimate eCommerce solution.

Alfresco
http://www.alfrescosoftware.com/
Alfresco is the leading open source alternative for enterprise content management. It is the first company to bring the power of open source to the enterprise content management market, enabling unprecedented scale, ease-of-use and a much lower total cost of ownership than proprietary systems. Alfresco aims to provide an open source offering that surpasses commercial offerings in terms of features, functionality and benefits. Alfresco is founded by a team of content management veterans that includes the co-founder of Documentum, John Newton former COO of Business Objects, John Powell and Dr. Ian Howells former Worldwide VP Marketing SeeBeyond.

Pentaho
http://www.pentaho.org
Pentaho provides the full spectrum of business intelligence tools, from reporting to analysis, dashboards to data mining. Pentaho’s technology supports a wide range of business initiatives, including sales and profitability analysis, customer analysis, HR reporting, financial reporting, KPI dashboards, supply chain analytics and operational reporting.

Typo3

www.typo3.org

Typo3 is a free Open Source content management system for enterprise purposes on the web and in intranets. It offers full flexibility and extendability while featuring an accomplished set of ready-made interfaces, functions and modules.

vTiger

www.vtiger.com

vTiger is a Customer Relationship Manager (CRM) capable of managing Accounts, Contacts, Products (Inventory Management), Invoices, Creating FAQs for Self Service Helpdesk etc. vTiger is based on the Open Source License and there are a number of tools/extensions available for vTiger which will improve your business productivity.