Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
Community Questions for Confluence - Keep questions and answers in one place with an engaging, community-driven Q&A discussion forum, powered by Confluence
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.
Question2Answer - A Q&A site helps an online community to share knowledge.
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
Stack Overflow for Teams - Everything you love about Stack Overflow in a private space.