Awesome Headless CMS 
Articles
What is a Headless CMS? by @chriscoyer
Headless and decoupled CMS: the essential guide by @contentiful
Content as a Service (CaaS): Decoupled CMS and Headless CMS 101 by @eZSystems
Decoupled CMS: Why “Going Headless” Is Becoming So Popular by @getpantheon
The Nearly-Headless CMS by @dirtystylus
Creating The Right Headspace: Why Headless CMS's Are Wrong by @OneHippo
What are the examples of decoupled/headless CMSs? on @Quora
A Headless CMS Won't Solve All Your Woes by @cmswire
Two Headless CMS - Head to Head by @elektromin
Cloud-First Headless CMS: What It Is and Why You Should Use It by @cmscritic
What is a cloud-first headless CMS? by @kenticocloud
What is Headless or Decoupled CMS? by @biztechcs
Headless CMS: Advantages of the decoupled approach by @effectiveui
Should you Decouple? by @lullabot
Blackstar, the API-first, headless CMS built for developers by @liammclennan
The Ultimate Guide for Headless Content Management Systems by @cmsconnected
Built.io wants to challenge Drupal and WordPress with its headless CMS by @TechCrunch
Headless CMS by @jpkeisala
What is a headless CMS? by @Oshyn_Inc
Perch Runway 3 as a Headless CMS by @grabaperch
Decoupling with a Headless CMS
Headless CMS – just a fad? by @Just_Clarity
Headless vs. Decoupled CMS Architecture by @carsoncgibbons
Use Cases for a Headless CMS by @gadgetopia
Decoupled CMS is the New Black by @gadgetopia
Sitecore as a true headless CMS by @Sitecore
Documents
The Rise Of The Headless Content Management
System by @forrester
The case for headless CMS by @effectiveui
Speakerdecks
WordPress as a Headless CMS by @bronsonquick
Webinars
The future of the CMS by @InVisionApp
Love Your CMS by @alistapart
Videos
A Conscious Uncoupling: WordPress as a Headless CMS by @krissierae
Projects
Directus
Graph CMS
Blackstar CMS
Contentstack
Narwhal CMS
Cloud CMS
dotCMS
Contentful
ButterCMS
Buckets
prismic.io
Osmek
Webhook
CosmicJS
Perch Runaway