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.
Katana MRP - Katana Cloud Inventory gives you a live look at all the moving parts of your business — sales, inventory, and beyond. Combining a visual interface and smart real-time master planner, Katana makes managing inventory and manufacturing intuitive.
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
ESP - C language web framework.
Slack - A messaging app for teams who see through the Earth!
The Manager's Red Book - Other Retail