For a huge amount of Knowledge on how to repair and refurbish old computers:

GadgetUK164 (YouTube)

RetroManCave (YouTube)

The 8-Bit Guy (YouTube)

For great information on Retro Gaming and Computing:

Nostalgia Nerd (YouTube)

For the calculator section I have relied a lot on thanks to Serge.

For some of the images used throughout the site -