Raspberry Pi models
Raspberry Pi (1) Model A (256MB)
Pi Model A (256MB) specifications
PCB rev 2 (svg)
How to identify:
Connectors: 1xUSB, Composite-video (RCA), full size HDMI, 3.5mm audio out, full size SD card, Micro USB power, 26-pin GPIO-header
Raspberry Pi (1) Model B (256MB or 512MB)
Pi Model B (512MB) specifications
PCB rev 2 (svg)
How to identify:
Connectors: 2xUSB, Composite-video (RCA), full size HDMI, 3.5mm audio out, full size SD card, Micro USB power, 26-pin GPIO-header, ethernet
512MB versions are mostly those with mounting holes (rev 2 PCB)
References
Raspberry Projects
RPi Hardware
Pi History
Raspberry Pi (Wikipedia)
Raspberry Pi information
Official documentation
Raspberry Pi Documentation
Documentation / FAQs
How to determine CPU clock speed [forum topic]
Raspberry Pi clones
Orange Pi
Orange Pi
Banana Pi
Banana Pi
Banana Pi BPI-R1 (router)
Banana Pi BPI-R2 (router)
Banana Pi BPI-R64
SD-card images
BerryBoot v2.0 – bootloader / universal operating system installer
Tutorials
Sparkfun Raspberry Pi GPIO Tutorial
Raspberry Pi 4 – Getting Started
Setup a Raspberry Pi Web Server with Your Own .COM Using Google Domains