- https://www.freeservicemanuals.net/, formerly sharefx.com
- https://elektrotanya.com/, extensive collection of appliance schematics
- https://www.hifiengine.com/ schematics of hifi amplifiers
- https://w140.com/tekwiki/
- http://www.ko4bb.com/getsimple/index.php?id=manuals
- https://bama.edebris.com/ boat anchor manuals
- https://www.s-manuals.com/ and its list of abbreviated markings on SMD chips
- https://artekmanuals.com mostly Tek and HP manuals in good quality scans
- http://tim.id.au/blog/tims-laptop-service-manuals/
- https://manualzz.com/
- https://www.manualslib.com/
- https://archive.org/details/manuals archive.org: The Manual Library; (various topics)
- https://justgivemethedamnmanual.com/

- https://www.eevblog.com/forum/ and EEVblog on YT
- https://www.mikrocontroller.net/
- YouTube channel BigCliveDotCom: teardowns of devices with its schematics explained
- https://www.allaboutcircuits.com/textbook: Lessons in Electric Circuits is a comprehensive online textbook

- https://github.com/mvp/uhubctl smart USB hub per-port power control
- https://github.com/hathach/tinyusb USB stack for microcontrollers
- https://github.com/lvgl/lvgl: Embedded graphics library
- https://github.com/ska80/tinygl: a Small, Free and Fast Subset of OpenGL*