Websites that have a shopping cart or checkout page, either using a known ecommerce platform or a custom solution.
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.
GitHub Pages is a static site hosting service.
Gravatar is a service for providing globally unique avatars.
Modernizr is a JavaScript library that detects the features available in a user's browser.
Octopress is a static blogging framework.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.
Varnish is a reverse caching proxy.