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

Parakeet - Cloud-based phone system with mobile app, designed for teams

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

Convoso - Call center solution to covert leads faster

HelpScout - Help Scout is a simple, straightforward way to provide excellent support

KronoDesk - KronoDesk is a web-based help desk solution.