If you are looking for customer relationship management (CRM) applications, this report on Tech Source offers details on some of the best and most well-known free and open-source CRM applications available to businesses today.
"CiviCRM is an open source CRM software that calls itself a "constituent relationship management solution". From its project website, it is described as a powerful contact, fundraising and eCRM system that allow you to record and manage information about your various constituents including volunteers, activists, donors, employees, clients, vendors, etc. CiviCRM is web-based, internationalized, and especially designed to meet the needs of advocacy, non-profit and non-governmental organizations. It may be utilized either standalone, alongside Drupal and Joomla! content management systems (CMS), or SAAS (Software-As-A-Service). The standalone version is designed to work alongside other CMSs."