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
HubSpot - Grow Better With HubSpot: Software that's powerful, not overpowering. Seamlessly connect your data, teams, and customers on one CRM platform that grows with your business.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
ActiveCampaign - Integrated email marketing, marketing automation, and small business CRM. Send beautiful newsletters, setup behavioral based automations, and benefit from sales automation.
Olark - Real-time chat and monitoring of your website visitors through Google Talk and Jabber.
Pardot - Salesforce B2B marketing automation