Down ROMemory Lane
Calculators
Calc Stack ↗ — HP Calculator Puzzles
Genaille-Lucas Rods
Slide Rule
Arithmometer
MK-52
MK-85M
HP-16C
TI-84
Early Computers
PiDP-8 (PDP-8)
PiDP-10 (PDP-10)
PiDP-11 (PDP-11)
KIM-1 / PAL-1
Altair 8800
IMSAI 8080
8052 Minicontroller
TRS-80
TRS-80 Model 100
TRS-80 PC-3
And / Or
Kaypro
Poqet PC
Sinclair ZX
Enigma Machine
Calc Stack ↗ — HP Calculator Puzzles
Calc Stack is an external calculator site — see the link above.