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.
TaskPaper - Plain text to-do lists for Mac
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.
Magnetic - Magnetic is an all-in-one agency management software built for productivity.
MockServer - Easy mocking of any system you integrate with via HTTP or HTTPS.