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.
MEE6 - MEE6 is a multipurpose Discord bot with moderation capabilities, leveling, Twitch alerts, and an easy-to-use online dashboard.
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
YAGPDB - YAGPDB (Yet Another General Purpose Discord Bot) is an advanced configurable Discord bot providing a load of features for help with managing a server.
Slack - A messaging app for teams who see through the Earth!
Arcane - Leveling, XP, ranks, voice, role rewards, auto mod, reaction roles, custom commands, YouTube alerts.