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

Survicate - Collect feedback on your website and find out more about your visitors.

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

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

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

UserReport - Free online usability surveys with demographic information. Detailed click tracking for websites and feedback button for online user forum. Easy signup.