opentaps Open Source ERP CRM Enterprise Resource Planning and Customer Relations Management Manufacturing Software.

SugarCRM is a customer relationship management (CRM).
SugarCRM is available under a commercial as well as an open source license.

vtiger CRM is an open source CRM software mainly for small and medium businesses to manage Salesforce, Customer Support, Inventory Management and other requirements. vtiger CRM also provides plug-ins for MS Outlook, MS Word, and Thunderbird.

webERP is a complete web based accounting/ERP system that requires only a web-browser and pdf reader to use. It has a wide range of features suitable for many businesses particularly distributed businesses in wholesale and distribution. It is developed as an open-source application and is available as a free download to use. The feature set is continually expanding as new businesses and developers adopt it.
There have been in excess of 80,000 downloads to date.

The Apache Open For Business Project is an open source enterprise automation software project licensed under the Apache License Version 2.0. By open source enterprise automation we mean: Open Source ERP, Open Source CRM, Open Source E-Business / E-Commerce, Open Source SCM, Open Source MRP, Open Source CMMS/EAM, and so on.

ERP5 is a full featured high end Open Source / Libre Software solution published under GPL license and used for mission critial ERP / CRM / MRP / SCM / PDM applications by industrial organisations and government agencies.

GNU Enterprise (GNUe) is a meta-project which is part of the overall GNU Project. GNUe's goal is to develop enterprise-class data-aware applications as Free software.

Compiere open source ERP software solutions and CRM software solutions provides full ERP and CRM functionality for distribution, accounting, inventory and service industries.

SQL-Ledger® ERP is a double entry accounting/ERP system. Accounting data is stored in a SQL database server, for the display any text or GUI browser can be used. The entire system is linked through a chart of accounts. Each item in inventory is linked to income, expense, inventory and tax accounts. When items are sold and purchased the accounts are automatically updated.

osCommerce is an Open Source based online shop e-commerce solution that is available for free under the GNU General Public License. It features a rich set of out-of-the-box online shopping cart functionality that allows store owners to setup, run, and maintain their online stores with minimum effort and with no costs, fees, or limitations involved.