KeyNexus - KeyNexus is a cloud-based encryption-key storage and provisioning service purpose-built for developers of cloud-based applications.
Dogtag PKI - The Dogtag Certificate System is an enterprise-class open source Certificate Authority (CA).
EnvKey - Protect API keys and credentials. Keep configuration in sync everywhere.
Authy - Best rated Two-Factor Authentication smartphone app for consumers, simplest 2fa Rest API for developers and a strong authentication platform for the enterprise.
Vault by HashiCorp - Tool for managing secrets
KeePass - KeePass is an open source password manager. Passwords can be stored in highly-encrypted databases, which can be unlocked with one master password or key file.