HelpScout - Help Scout is a simple, straightforward way to provide excellent support
SupportYourApp - Connecting talented people with the blooming IT industry to help them grow faster by outsourcing support.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
SiteGlue - SiteGlue AI Powered Live Chat + Business Text Messaging
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
nService - Web based help desk software that helps you help your employees and customers. Easy to use. Customizable. Free trial.