Amazon Cognito - Amazon Cognito lets you add user sign-up, sign-in, and access control to your web and mobile apps quickly and easily. It scales to millions of users and supports sign-in with social identity providers and enterprise identity providers via SAML 2.0.

TypingDNA Authenticator - 2FA codes in your browser, secured by the way you type

Stripe - Online payment processing for internet businesses. Stripe is a suite of payment APIs that powers commerce for online businesses of all sizes. Use Stripe’s payment platform to accept and process payments online for easy-to-use commerce solutions.

PropelAuth - PropelAuth hosts and manages your authentication.

Authorizer - Authorizer is an open-source authentication and authorization solution for your applications.

ServiceBot - The new, open source way to run a business online. Subscription billing, Self-service customer portal, service lifecycle management?