Founders Nation - Find or become a startup cofounder
Huntathon - Browse and submit Product Hunt Global Hackathon projects
CoFoundersLab - Meet 250,000+ entrepreneurs online
Co-founder Question Cards - Questions to ask your co-founder to know each other better.
Hackathon Match - Find collaborators for the Product Hunt Global Hackathon
CollabFinder - Find cofounders and makers to help build your project