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

EssentialPIM - EssentialPIM is a free Personal Information Manager that keeps up with the times and lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.

Twilio Studio - Accelerate your customer engagement roadmap

Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.

Froged - One click solution providing easy-to-use marketing, sales and support services to turn website visitors into happy customers.

Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.