I’m Tomu, a tiny ARM microprocessor which fits in your USB port. I have two buttons and two LEDs!
I’m fully open source and am buildable by hobbyists! Designed for 2-factor authentication, USB experiments, or anything else you can think of.
Can be used as U2F/FIDO authenticator, but has no AES hardware accelerator.

Software runs on Linux, Android, OS X, iOS and Windows.

Prototype of a translator from a python-like syntax to C. Found via
https://www.jwz.org/blog/2017/04/python-has-a-lot-to-fucking-answer-for/#comments

On http://xed.ch/help/, a number of useful personal technical notes can be found.

For example, http://xed.ch/help/usbdrive.html describes how to create bootable USB drives.

From the author:
"I was looking for a simple way to backup data on Android devices directly to a device running GNU/Linux connected over a USB cable (in my case, a desktop computer).

Is this really so unique that it’s worth writing a new article about it? Well, in my case, I did not want to buffer the data on any “intermediate” devices such as storage cards connected via microSD or USB-OTG. Also, I did not want to use any proprietary tools or formats. Instead, I wanted to store my backups in “oldschool” formats such as dd-images or tar archives. I did not find a comprehensive howto for that, so I decided to write this article."

piShift makes it super simple to get programming on your Pi Zero – just plug your Pi into your laptop with a micro-USB cable and it appears as a USB Drive. Drag across a .py file, and within seconds the Pi will automatically detect it’s been added, and will start running the most recently edited file.

V-USB is a software-only implementation of a low-speed USB device for Atmel’s AVR® microcontrollers, making it possible to build USB hardware with almost any AVR® microcontroller, not requiring any additional chip.

USB oscilloscope, logic analyser, waveform & pattern generator.

A Libre * Design, Minimalist, Ergonomic, Splittable, Symmetric, Compact 64 Keys, Eco-Friendly, Durable, Native Colemak Keyboard, Embedded Mouse and Firmware Programmable USB Keyboard.

OpenVizsla is an open source, high-speed USB sniffer that will help decode, debug and hack proprietary USB hardware devices.

Neat hardware authentication device.