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

InsightSquared - #1 for Salesforce.com Pipeline forecasting, profitability analysis, activity tracking: all the small business intelligence you need. Works using CRM data and automatic syncing.

Maian Support - Free responsive PHP Helpdesk System

Aviso - Aviso provides predictive analytics software to help sales organizations optimize their performance and exceed revenue goals using machine learning algorithms and portfolio management techniques.

Zendesk - Zendesk is a beautiful, lightweight help-desk solution.

Sidekick by Hubspot - Customer insight integrated with your email tools.