Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Jenkins - Jenkins is an open-source continuous integration server with 300+ plugins to support all kinds of software development
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
CircleCI - CircleCI gives web developers powerful Continuous Integration and Deployment with easy setup and maintenance.
Slack - A messaging app for teams who see through the Earth!
Travis CI - Focus on writing code. Let Travis CI take care of running your tests and deploying your apps.