Todoist - Todoist is a to-do list that helps you get organized, at work and in life.

Beeceptor - Unblock yourself from API dependencies, and build & integrate with APIs fast. Beeceptor helps you build a mock Rest API in a few seconds.

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

Webhook.site - Instantly generate a free, unique URL and email address to test, inspect, and automate (with a visual workflow editor and scripts) incoming HTTP requests and emails.

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.

MockServer - Easy mocking of any system you integrate with via HTTP or HTTPS.