Zabbix - Track, record, alert and visualize performance and availability of IT resources
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
HelpScout - Help Scout is a simple, straightforward way to provide excellent support
Checkmk - Checkmk - the software for effective IT monitoring