Influences

I've spent hours reading or listening to these people. I consider each of them to be leading experts in their field and great at communicating that expertise. The people on this list have been significant to my development and I recommend their work.

Embedded Electronics & Firmware

Phil Koopman
Elecia and Chris White
Phillip Johnston
Jack Ganssle
Michael Barr
John Regehr
Ken Shirriff

Software Development

Joel Spolsky
Jeff Atwood
Scott Hanselmann
Raymond Chen
Michael Lopp

Security & Encryption

Mikko Hyponnen
SwiftOnSecurity
Alan Woodward
Rik Ferguson
Bruce Schneier

Science and Skepticism

Carl Sagan
Isaac Asimov
Steven Novella
James Randi
Jim Al-Khalili
Phil Plait
Ben Goldacre
Simon Singh
Sean Carroll

Philosophy

Daniel Dennett
Massimo Pigliucci
Alex Malpass
Matt Dillahunty
Julian Baggini

Psychology

David McRaney
Oliver Burkeman
Richard Wiseman
Chris French

Worth Following on YouTube

Whilst some of these are not quite at the level of those listed above, these channels are recommended:

Electronics

SDG Electronics - Steve Gardner
EEVblog - Dave Jones
Marco Reps
GreatScott!
Kiss Analog - Eddie Aho
w2awe - Alan Wolke at TekTronix
VoltLog
mikeselectricstuff - Mike Harrison at White Wing Logic
Cybergibbons - Andrew Tierney at PenTestPartners
The Signal Path - Shahriar Shahramian
Prof Sam Ben-Yaakov - Professor at Ben Gurion University

Embedded Firmware

Phil Koopman - Associate Professor, Carnegie Mellon University
Quantum Leaps, LLC - Dr. Miro Samek

Software Development Process & Management

Healthy Software Developer - Jayme Edwards