AddThis is a social bookmarking service that can be integrated into a website with the use of a web widget.
AWeber is an email marketing service.
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.
Open Graph is a protocol that is used to integrate any web page into the social graph.