The authors distribute the textbook for free at https://pages.cs.wisc.edu/~remzi/OSTEP/.
Aquinas is an interactive learning system that aims to teach computer programming and exploit development.
The C Programming Language
Deep C provides some surprising details about the C programming language.
A Guide to Undefined Behavior in C and C++ dives into C’s undefined behavior.
Intel publishes a number of manuals describing their architecture. Volume 3 is the Systems Programming Guide:
The Unix Command Line
Welcome to the Linux command line for you and me! provides an introduction to the Linux command line.
UW–L Computer Science Department technology notes provides information about how to use the computing facilities provided by the UW–L Computer Science Department.