HeySpace - HeySpace is the only free task and simple project management software with communication and collaboration feature.
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Slack - A messaging app for teams who see through the Earth!
tawk.to - tawk.to is a free live chat app that lets you monitor and chat with visitors on your website or from a free customizable page
Skarpline - Skarpline provides centralized enterprise messaging, link sharing and file management to improve productivity.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.