Doorkeeper is an OAuth 2 provider for Ruby on Rails / Grape
FIDO® Certified StrongKey FIDO Server (SKFS)
PHP strong authentication library, web interface & CLI, OATH certified
Zentyal is a Linux Small Business Server
apache cookie SSO mechanism.
hook pam to authenticate users against anything
Apache LDAP Directory Manager
NTLMv2 authentication library and filter for Java
Authentication, Access Control, and Single Sign-On
Open Source Web Single Sign-On
LDAP backend for VirtualBox RDP Auth
Deprecated project - see http://wordpress.org/extend/plugins/wpmuldap/