Google Titan - A 2FA device to protect yourself from hackers
Base API - API for authentication, email sending, images and more!
Hydro Mobile App - Free, instant, scalable, blockchain-based 2FA security
Two Factor Auth (2FA) - List of websites and whether or not they support 2FA
TwoBlocks - A 2FA provider on BlockStack
Castle - The easiest way to protect your users from getting hacked