DanielOpen-Source Joystick: OSA 2-Button Stick now available for pre-order
The OSA Stick ("Open Source Arcade Joystick") aims to be an "affordable and modular open-source arcade joystick that anyone can assemble at home and customize to their needs." The documentation is available on GitHub.
A variant of the stick with a case designed to more closely resemble the classic "Competition Pro" design is now available for pre-order at Dragonbox.