Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Kayako - Help Desk Software and Customer Service Software by Kayako. Improve customer satisfaction, increase sales.
ThriveDesk - Helping startups thriving customer support
Service - Customer service issues solved for you, on demand, for free.
Kommunicate - Customer support automation platform with live chat and chatbots