Slack has channels for OSC project teams and sprints. OSC communication happens in the Salesforce-External slack organization.
Quip stores artifacts from sprints, like schedules and participant lists.
Zoom is the videoconferencing tool used for OSC projects and events. Download the latest Zoom client.
Use the Trailblazer Community to discuss projects in a larger community forum. The best place to get started is Open Source Commons and Community Sprints. Many project teams also have their own Chatter groups in the Trailblazer Community.
Find social posts with the hashtag #SFDOsprint.