A boot selector for the Raspberry Pi. Interactively pick, download, and install multiple OSes for the RasPi to the same SD card. The selection can be changed later. Also lets you use USB drives for storing those OSes instead of an SD card. HDMI enabled.
This GPIO Pinout is designed to be both a quick and interactive reference to the Raspberry Pi GPIO pins, plus a comprehensive guide to your Raspberry Pi's GPIO interfaces. It also includes dozens of pinouts for Raspberry Pi add-on boards, HATs and pHATs.
Blue Dot allows you to control your Raspberry Pi projects wirelessly - it's a Bluetooth remote and zero boiler plate Python library. Makes it easy to use Bluetooth. Has excellent documentation, including how to pair your RasPi with your phone from the command line. Seems to work pretty well. Bluetooth interface is only up while BlueDot.wait_for_press() is running. Has a serial communications API, also, for sending and receiving arbitrary data.
I don't see why this module couldn't be used more generically to interact with arbitrary Linux boxen over arbitrary Bluetooth interfaces. HCI is HCI, right?
The matching Android app is in the Play store. There is even a version of the Bluedot app written in Python that you can use from the desktop to interact over Bluetooth.
Requires that the dbus-python module be installed to the same venv. Also requires that the shell running the Python interpreter have sufficient access privileges to interact with the Bluetooth interface (root certainly works), usually the bluetooth group.
A general purpose radio frequency transmitter for Raspberry Pi which doesn't require any other hardware unless filter to avoid intererence. It can handle frequencies from 5 KHz up to 1500 MHz. Plug a wire into GPIO pin 4 (hardware pin 7) and it'll broadcast just about whatever you tell it to. Has an installation script. It's recommended that you use a bandpass filter to minimize noise on the air. Works with just about every RasPi (except the B). Has a text based menu to control it. Defaults to 434 MHz (international free ISM band). You can even broadcast spectrogram pictures! Can even do POCSAG to activate pagers!
Broadcom opensourced the GPU drivers for the RaspberryPi under a three-clause BSD license. The code is fully functional, hasn't been reverse engineered, and can be compiled and used imediately on the RasPi.