AddThis is a social bookmarking service that can be integrated into a website with the use of a web widget.
Authorize.net is a secure online payment gateway service that enables businesses to accept payments through various channels, such as ecommerce websites, mobile devices, and retail stores, providing a trusted platform for processing credit card and electronic cheque payments.
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.