Collabtive – cloud-based groupware.

eGroupware

SugarCRM

VTiger

Magento eCommerce Community Edition

dotProject – open source project management tool

GanttPV – Project scheduling software (scriptable, cross-platform, and open source).

Open Business Management (OBM) – free and open source messaging and collaboration software (GPL v3). Groupware, messaging, CRM, LDAP, domain management, smart-phones and PDA synchronization.

Redmine – flexible project management web application written using Ruby on Rails framework. Cross-platform, cross-database, GPL v2.

Task Juggler – Free and Open Source Software project management tool.