Founders Nation - Find or become a startup cofounder
Requests for Startups - A place to discover ideas that VCs & angels want to fund
CoFoundersLab - Meet 250,000+ entrepreneurs online
Twittr Gems - Discover and read the best Twitter threads
Findnlink - Find people to work with on your ideas.
Entrepreneur List - A curated library of entrepreneurship knowledge to help entrepreneurs grow a business.