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.
Optimizely is an experimentation platform that helps developers build and run A/B tests on websites.
Quantcast Measure is an audience insights and analytics tool.
ShareThis provides free engagement and growth tools (e.g., share buttons, follow buttons, and reaction buttons) for site owners.