Links
3D printing
Re-purposing old devices
Windows for ARMv7 - run full Windows desktop on an old Lumia phone
Repurposing dodgy Android TV boxes as Linux boxes
Local cell networks using a VGA adapter (!) - might be possible to revive old 1G/2G cell phones
Installing a Nexus tablet in the car dash (outdated, of course, but still cool)
Original Samsung Galaxy has video out on the audio jack
Electronics
Infinite Firefly - solar powered LED flasher
Z80 TV Game - console from scratch
Raspberry Pi Zero as a USB gadget (storage, keyboard, network)
USB keyboard using Adafruit Trinket
Macchina - microcontroller with OBD2 connector, WiFi and Bluetooth
Hosting
Software
navit navigatwdfsddfion software - runs on a potato
WeatherStar 4000+ weather forecast TV channel emulation
LinuxPhoneApps - for your PinePhone, Librem5, FLX1, and others
AWBfL - independent browser based on WebKit2 (fork of original Midori)
Sites
Tutorials
Lode's Computer Graphics Tutorial - used in my Dark Streets FPS
Other interesting stuff
Drive On Wood - vehicles converted to woodgas