Here are some links that I have found worthwhile enough to share.
They are in no particular order.
Magnetic Logic
Jeri Ellsworth
https://www.youtube.com/watch?v=p7SkE5pERtA
Interesting girl talking about interesting idea.
Operating Systems: Three Easy Pieces
Remzi H. Arpaci-Dusseau and Andrea C. Arpaci-Dusseau
http://pages.cs.wisc.edu/~remzi/OSTEP/
Free online book about operating systems inluding thread programming and synchronization concepts
The Scientist and Engineer's Guide to Digital Signal Processing
Steven W. Smith
http://dspguide.com/
Free online version of introductory DSP book. The number one starting point when beggining DSP journey.
Website of Julius Orion Smith III
https://ccrma.stanford.edu/~jos/
It contains materials (online books) about mathematical background of DSP including
MATHEMATICS OF THE DISCRETE FOURIER TRANSFORM (DFT) WITH AUDIO APPLICATIONS at
https://ccrma.stanford.edu/~jos/mdft/
Khan academy
https://www.khanacademy.org/
Website that contains many teaching materials of varying level of quality.
Especially math lessons are good and they start from the level of adding single digit
numbers and go up to integrals.
Blausen Medical
http://blausen.com/
3D animations and explanations of human anatomy.
Especially interesting for audio DSP is ear category.