OpenStax Physics has free e-texts for high school (roughly equivalent to GS104), college (algebra-based), and university (calculus-based) physics
Khan Academy has physics videos
PhET from the University of Colorado has numerous excellent physics simulations
Veritasium has some excellent physics videos on YouTube, though not always directly related to the content of courses I teach
Crash Course Physics has relevant videos on YouTube
Coursera offers free online physics classes
MIT Open Courseware has free physics videos and lecture notes