Getting Started in Electronics, by Forrest M. Mims, III (PDF, 128 pages.)
An excellent introduction to electronics, with amusing but helpful diagrams.
It's a bit old (circa 1983-1994), but it's still great information. The fundamentals never change.
Electronics Basics by Rohm Semiconductor
Ham Test Online
A huge web site devoted to teaching all about ham radio.
Naval Electrical Engineering Training Series
"Oldest, most comprehensive electronics course in existence." (W5YI Technician Class Preparation book)
Randy Hall's, K7AGE, YouTube Channel.
Hundreds of videos on many topics, such as Getting Started on 2 Meters, Introduction to PSK31, Sound Card Interfacing, Ham convention reviews, and many more.
David Casler's YouTube Channel: Ask Dave and Ham Radio Answers
The Ask Dave series answers questions of particular interest to new hams. The Ham Radio Answers series includes videos for Technician, General, and Amateur Extra training, closely following the ARRL License Manuals
All About Circuits
Numerous articles on different types of circuits from a professional technical media company.
Amateur Radio and Emergency Communications
(A very good description of amateur radio's role in emergency communications.
Thankx to Ella Johnston and her mother Elaine for the suggestion.)