Favorites

ESP32

ESP-WROOM-32
ESP32 Datasheet - v2.4
ESP32 Technical Reference Manual - v2.9
ESP IDF Programming Guide - Latest
ESP IDF Programming Guide - v2.1
ESP Toolchain for Windows
ESP IDF (GitHub)
ESP Serial Bootloader (GitHub)
ESP Boot Mode Selection (GitHub)
ESP Serial Bootloader Utility (GitHub)
ESP Forums (Espressif)
ESP with JTAG
ESP debugging with JTAG (GoJimmyPi)
ESP Internet of Things (Links)

FreeRTOS
Visual GDB (SysProgs)

Raspberry PI

RaspberryPI.org
Pinout Guide

BeagleBone

BeagleBoard.org

Others

ARM mbed - Developer site
Embedded Artists - The Art of Embedded Systems Development Made Easy
Arduino
NXP Microcontrollers
Arduino Projects (on All About Circuits)

PC Boards

USA

Pad2Pad - PCB Manufacturer    (Facebook)
OSHPARK - We make perfect purple PCBs promptly

China

Seeed Studio - Fusion PCB & PCB Assembly & Flexible PCB    (Facebook)
JLCPCB - PCB Prototype & PCB Fabrication Manufacturer    (Facebook)
PCBCart - PCB Manufacturing and Assembly All in One Place    (Facebook)
Gold Phoenix - PCB board manufacturing, PCB prototyping service & PCB assembling services
PCB-POOL Prototype
PCBWay PCB Prototype the Easy Way    (Facebook)