Open source support ticket system simple, free, lightweight, open source, and easy to setup and use.

Vtiger CRM is online customer relationship management software that helps you track and nurture customers across marketing, sales, and customer service.

PHPBack is an open source feedback system.

Helprace is a customer service software suite linking a ticket system with help desk software.

Trakdesk is a fully customizable customer support platform with all the bells and whistles you would need to provide exceptional customer support.

Kayako is a customer service software.

Brimir is an Open source ticket manager.