Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.

UseResponse - Open-source, self-hosted customer feedback software, live chat and helpdesk system that you can install on your server. Organize documentation using knowledge base and get feedback from social networks with centralized system

Crisp Chat - Multi-channel customer support software

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

Chatlio - When you have a business to run, your average instant messaging software just will not do. You need an internal presence upon which your entire team can collaborate on. Read more about Chatlio.

ChatWoot - Open-source omnichannel customer engagement platform