MyITCRM – Free and Open Source CRM Software.
QWcrm – Free and Open Source CRM Software.
Kimai v1 open source time-tracking - please switch to Kimai v2
Open Source CRM for Enterprise
OroCRM - an open-source Customer Relationship Management application.
eLitius is a free open source affiliate tracking software. Lots of features, customizable templates using Smarty. PHP/MySQL.
SuiteCRM - Open source CRM for the world
MyBB is a free and open source forum software.
Mautic: Open Source Marketing Automation Software.