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

Novocall - Novocall converts web visitors into sales calls in seconds.

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

OptinMonster - OptinMonster helps to convert abandoning website visitors into subscribers and customers.

JivoChat - JivoChat is a live chat that enables you to talk to visitors on your website

Callpage - Turn website visitors into sales calls. Use CallPage and provide immediate free phone callback to your leads in 28 seconds.