I discovered some tools which you may find interesting. Here is the list.

1. Taskade

Taskade is a simple way to make task lists, capture your ideas, and stay organized. Instantly share your lists and collaborate with your friends, family, and teammates.

Link: Taskade

2. Postal

Postal is a open source and fully featured mail server for use by websites & web servers.

Github: Postal

3. React Sketch.app

React Sketch.app is a open source library that allows you to write React components that render to Sketch documents. It is a tool which built to help bridge the gap between designers and engineers working on design systems at scale.
Read more: here

Link: React Sketch.app

4. fake{JSON}

It is designed to be an always ready, always available, mock backend for your application. You can use the API for you frontend development, end to end testing, regression testing, rapid prototyping, data generation, and more. Use the API to iterate, update, and refresh your application for consistent and dependable mock data.

Link: fakeJSON

5. Figma

Figma is the first interface design tool based in the browser, making it easier for teams to create software.

Link: Figma

6. Kur

Kur is open source system for quickly building and applying state-of-the-art deep learning models to new and exciting problems. Kur builds on top of Keras to provide a descriptive framework for designing and running deep learning models.

Github: Kur

7. Maildrop

MailDrop is an open-source, scalable, high-performance version of Mailinator, a "temporary inbox" that you can give out when you don't want to give out your real e-mail address. MailDrop inboxes are designed to be quick and disposable.

Link: MailDrop
Github: Maildrop

8. Sizzy

A tool for testing responsive websites crazy-fast.

Link: https://sizzy.co/

9. Probot

A framework for building GitHub Apps to automate and improve your workflow. GitHub Apps can listen to webhook events sent by a repository or organization. Probot uses its internal event emitter to perform actions based on those events.

Link: Probot
Github: Probot

10. Spell

Infrastructure for AI and Deep Learning.
Documentation: Spell

Link: spell.run

11. Safecopy

It is a data recovery tool which tries to extract as much data as possible from a problematic (i.e. damaged sectors) source like floppy drives, hard disk partitions, CDs, tape devices, where other tools like dd would fail due to I/O errors.

Link: Safecopy