Fastly is a cloud computing services provider. Fastly's cloud platform provides a content delivery network, Internet security services, load balancing, and video & streaming services.
Font Awesome is a font and icon toolkit based on CSS and Less.
GitHub Pages is a static site hosting service.
MathJax is a cross-browser JavaScript library that displays mathematical notation in web browsers, using MathML, LaTeX and ASCIIMathML markup.
Modernizr is a JavaScript library that detects the features available in a user's browser.
Typekit is an online service which offers a subscription library of fonts.
Varnish is a reverse caching proxy.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.