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.
Submit Checklist - Checklist of directories to submit your startup
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
Manager checklist - Cheatsheet of things every manager should do
Slack - A messaging app for teams who see through the Earth!
Checklistomania - Centrally managed todo lists for complex processes