cdnjs is a free distributed JS library delivery service.
Disqus is a worldwide blog comment hosting service for web sites and online communities that use a networked platform.
Google Analytics is a free web analytics service that tracks and reports website traffic.
MediaWiki is a free and open-source wiki engine.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
PayPal is an online payments system that supports online money transfers and serves as an electronic alternative to traditional paper methods like checks and money orders.
PHP is a general-purpose scripting language used for web development.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.