TypingDNA Authenticator - 2FA codes in your browser, secured by the way you type
OpenID Connect Playground - Learn about the standard behind Google SSO
PropelAuth - PropelAuth hosts and manages your authentication.
Amazon SSO - Manage access to multiple AWS accounts & business apps
Authorizer - Authorizer is an open-source authentication and authorization solution for your applications.
FusionAuth - FusionAuth is a CIAM platform that is 100% free for unlimited users.