UseGravity.App - Build a Node.js & React app at warp speed with a SaaS boilerplate
Auth0 - Auth0 is a program for people to get authentication and authorization services for their own business use.
MERNKIT - SaaS Boilerplate for MERN Stack - MongoDB, Node.js, React.js - Stripe, Authentication, User Management, Beautiful UI - Focus on features!
Firebase Authentication - Application and Data, Application Utilities, and User Management and Authentication
SaaSBox - Everything you need to jumpstart and run your SaaS in one turnkey package. Save months launching and running a SaaS
OmniAuth - OmniAuth is a flexible authentication system utilizing Rack middleware.