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.
Better Notes - Simple notes app that ties notes together with #hashtags
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
Whimsical - The visual workspace for teams.
Slack - A messaging app for teams who see through the Earth!
Great F*cking Startup Advice - Strongly worded suggestions for startup founders