Ben Crowell, a teacher at Fullerton College, provides great, free physics and astronomy educational resources at this website. The Physics link offers three well written, downloadable introductory physics textbooks --...

All About Circuits is a website that “provides a series of online textbooks covering electricity and electronics.” Written by Tony R. Kuphaldt, the textbooks available here are wonderful resources for students,...

This free physics textbook from Boundless Learning is based off openly available educational resources such as "government resources, open educational repositories, and other openly licensed websites." The textbook...

This online textbook by Glenn Elert contains explanations, examples, and practice problems for many topics in introductory physics. These topics include Mechanics, Matter, Thermal Physics, Waves & Optics, Electricity &...