jQuery is a JavaScript library which is a free, open-source software designed to simplify HTML DOM tree traversal and manipulation, as well as event handling, CSS animation, and Ajax.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Pantheon is a WebOps (Website Operations) and Management Platform for WordPress and Drupal.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.
Varnish is a reverse caching proxy.