Linkedin Sign-In is an authentication system that reduces the burden of login for users, by enabling them to sign in with their Linkedin account.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Piwigo is an open-source photo management software designed for creating and managing online photo galleries.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.