Founders Nation - Find or become a startup cofounder
Fusebot - Write custom commands to integrate anything on Slack/Discord
CoFoundersLab - Meet 250,000+ entrepreneurs online
Invision - Prototyping and collaboration for design teams
Findnlink - Find people to work with on your ideas.
zipBoard - ZipBoard is a web-based visual bug tracking & issue tracking tool that helps developers, testers and project managers collaborate during website and elearning development.