The following resources are broken down into 3 primary sections, ServiceNow, JavaScript, and Software Development. Each resource has a resource type found within [square brackets].
ServiceNow
General
dylanlindgren.com [blog]
blog.jacebenson.com [blog] - a great aggregate resource for all things ServiceNow
Knowledge '19 On Demand Library [resource]
ServiceNow Fundamentals [video collection] - a great YouTube playlist of ServiceNow fundamentals videos
ServiceNow Standards Framework [resource] - ServiceNow framework to get you started on a number of different topics
Interface Design Patterns for Script Includes [blog post] - best practices around script include development
Script Execution Order [article] - excellent resource that exposes the ServiceNow execution order of scripts and various engines
Script evaluation of fields by data type [article] - another excellent resource which explores the evaluation of fields by data type in ServiceNow scripts
Understanding GlideAjax [blog post] - a deep dive into GlideAjax
GlideAjax Examples [tutorial/guide] - more GlideAjax examples, because… who starts from scratch? 🙂
GlideAjax Troubleshooting [blog post] - having trouble with your script include? Checkout this blog post
Using GlideRecordSecure [article] - product docs page on GlideRecordSecure
Script Include Best Practices [blog post] - learn how to create script includes the proper way
Bypass SSO [community] - general SSO information
Glider [library] - an interesting library with tons of awesome features
Useful ServiceNow Snippets [snippets/code] - a list of common ServiceNow snippets to help reduce frustrations
Demystifying the ServiceNow Cloud [video] - an interesting look into how ServiceNow manages their architecture
Service Portal
Understanding Service Portal [article] - product documents page with video
ServiceNow Solution Innovation Library [resource]
Service Portal and client scripts [article]
Embedded widgets [article]
Building Multilingual Service Portals [blog post]
Service Portal fundamentals: AngularJS scopes [blog post]
Widget developer guide [guide]
Recommendations for developing widgets [article]
Tutorial: Build a custom widget [tutorial]
SCSS functions [article]
Understanding Scope [blog post] - a great community article on the concept of scope in ServiceNow
Service Portal redirects [community] - understand how Service Portal redirects work
JavaScript
Introductory
Mozilla Developer Network [resource] - your best friend
codecademy [course] - a great free resource to help you get started with JavaScript
Code School [course] - a great premium resource
The Odin Project [course] - tons of great content here
freeCodeCamp [course] - another great free course
Eloquent JavaScript [book] - one of my personal favorite JavaScript books, and the online version is FREE
JavaScript Enlightenment [book]
JS Books [book]
50 Best JavaScript Resources [aggregate]
JS for Cats [resource] - why not?
Null vs Undefined [blog post]
Advanced
JavaScript Engines: How Do They Even Work? [blog post]
Functional-ish JavaScript [blog post]
Design Patterns Game [resource]
In Defense of the Ternary Statement [blog post]
How JavaScript works [blog post]
16 JavaScript Concepts You Must Know Well [resource]
The Weird Parts [resource]
7 Useful JavaScript Tricks [blog post]
Design patterns in modern JavaScript development [blog post]