I use Trello to track my personal tasks and anything I assign to my team (although they get to figure out how to track those tasks in their own way).

+1 to sandmansandine for using Slack's channels to segregate communication about parts of your business.

We use Github Wiki for a product development overview and github issues for actionable tasks. So the wiki is its own private repo and has issues about adding knowledge etc, the issues are in each project's repo.