Blender official release and some specialty builds:
Blender official release - v2.79 is current
OpenHMD/Virtual Reality development branch of Blender
NOTE: The MORSE branch download and setup information is on their webpage listed below. It is based on Blender v2.69 and runs in Linux and OS X.

Youtube has some great video tutorials. Here are some of the best starting points:
At Mind's 101 Kids - for young students aged 10 and older
CG Cookie's Intro to Blender - free and paid tutorials

Internal game engine for fast prototyping:
BornCG 'Blender Game Engine Basics' series
Game Engine Documentation

General Blender resources:
Blender online manual
Blender Nation blog
Blender Artist's forums - beware of trolls and search with an external engine
Blender Q&As on Stack Exchange

Add-on catalog and API reference:
Blender Wiki - see the sections in Add-ons

Robotics focused resources, general and Blender specific:
Open-source Robotics on Wikipedia - general reference
MORSE, the Modular OpenRobots Simulation Engine - generic simulator for academic robotics
The MORSE Simulator documentation - stable version docs

Easily run Linux/MORSE as an app on your computer in a virtual machine:
Virtual Box on Wikipedia
Platform info and downloads - install the extension pack also
NOTE: pay close attention to the MORSE hardware requirements and setting up the virtual machine guest to match closely. 2 or 3GB of RAM should work ok in a VM but use 4GB if you have 6GB of RAM or more on the host. Research graphics setups for VBox guests to get an optimized display setup.

Articles and background information driving the concept forward:
Digtial Twin on Wikipedia
General Electric research - multiple videos and blog posts
Gartner Digital Twin IoT research overview
Article: Forbes on digital twin technology
Article: Siemens on the value of the digital twin
Article: Crain's Chicago Business on being a digital twin architect
Article: Hannover Messe on digital twins, cobots and artificial intelligence
Article: The Economist on millions of things soon having digital twins

See Helpful Links page for more helpful information!