https://www.legroom.net/howto/wii
Wii hacking has become a hell of a lot easier since Nintendo abandoned the console and stopped pushing endless updates that stopped common hacks working without actually improving the console's functionality. And since the Wii Shop and all the online functionality has been discontinued too, hacking has become essential if you want to use the Wii's full capabilities.
Complete guides to homebrew and custom firmware for various devices.
Pretty comprehensive documentation of the Gameboy's hardware and that of related peripherals (eg the Gameboy Printer).

https://www.ifixit.com/Device/Eee_Pad_Transformer_Prime_TF201
Still the best tablet/laptop combo over 10 years later.

https://www.ifixit.com/Device/Asus_Eee_PC_1005HA
How to fix/maintain the most under-rated laptop of the last 20 years.
http://tuxnes.sourceforge.net/gamegenie.html
Game Genie codes. Like VideoPlus, but with more obfuscation.
https://projects.raspberrypi.org/en/projects/fart-detector
"All kids understand that farts are funny. As we grow older, some of us lose our sense of humour in this area. You’ll be glad to hear that we believe that building a real working fart detector has both educational and comedic value."
https://projects.raspberrypi.org/en/projects/build-your-own-weather-station
If you have some of the measuring implements for the Raspberry Pi Weather Station but not the HAT (which was only distributed to schools), then this page will show you how to actually use the damn things.

https://github.com/dresden-elektronik/deconz-rest-plugin/issues/405
Zigbee sniffing on the Raspberry Pi
https://www.raspberrypi.org/forums/viewtopic.php?t=23440
Banner for SSH logins

https://www.instructables.com/id/PiAnyWhere-4G-LTE-Hat-for-the-Raspberry-Pi


https://learn.adafruit.com/raspberry-pi-physical-dashboard?view=all
Making a funky 1970s-sci-fi-style readout with a Pi and some 7SDs/motors.
http://blog.soton.ac.uk/webteam/2014/01/31/location-independent-software
Blog post by TIDT.
https://www.cyberciti.biz/tips/linux-write-sys-v-init-script-to-start-stop-service.html

https://forum.xda-developers.com/transformer-tf700/development/rom-t3457417

https://forum.xda-developers.com/showthread.php?t=2627965
Kitkat ROM for Dad's tablet
https://m.bulbapedia.bulbagarden.net/wiki/Save_data_structure_in_Generation_III