Raspberry Pi — The little board that launched a thousand projects. Still the best single answer to "what hardware should I learn on?"

Adafruit — Limor Fried built the shop she wished had existed. Great hardware, great tutorials, genuinely good company ethics.

Open Source Ecology — Open-sourcing the 50 machines needed to build a small civilization from scratch. The most ambitious hardware project on earth.

BusKill — A dead-man switch for your laptop: pull the USB cable and the machine locks or wipes. Simple, open, and the threat model is real.

Tigard — A multi-protocol hardware hacking tool for JTAG, SPI, I2C, UART and more. Open hardware, built for people who want to know what their chips are actually doing.