cdnjs is a free distributed JS library delivery service.
D3.js is a JavaScript library for producing dynamic, interactive data visualisations in web browsers.
Flickity is a JavaScript slider library, built by David DeSandro of Metafizzy fame.
Google Analytics is a free web analytics service that tracks and reports website traffic.
JSDelivr is a free public CDN for open-source projects. It can serve web files directly from the npm registry and GitHub repositories without any configuration.
Mailchimp is a marketing automation platform and email marketing service.
Unpkg is a content delivery network for everything on npm.