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Notion - https://notion.so - wiki for orgs

Trello - https://trello.com - cards / prioritization

Figma - https://www.figma.com/ - interface design / wireframes

GitHub / Gitlab - source code server / pull requests

tmate - https://www.figma.com/ - share terminal over internet

I think the link for tmate should be https://tmate.io/

I have used dropbox paper to collab on things in realtime, but not sure what kind of reply you were looking for.

I think that it depend what you need to cooperate with.

Ask HN: Tools for Cooperation