FujiNet was intended to be a network adapter that attaches to the SIO (Peripheral) port of an Atari 8-bit computer system but has become an all encompassing SIO peripheral emulator. Designed to physically interface with any 8-bit Atari system via the SIO port with a 3d printed SIO plug. Also has an SIO jack on the back so that other peripherals can be plugged in as passthrough devices. Powered from the Atari (unless it's used on a 400 or 800, they don't supply enough current).
Emulates data storage on cassettes and floppy disks. Data can be stored on SD card or TNFS network share. Emulates the 850 modem. Emulates most of the common Atari printers, but converts files to PDF and saves them. Implements a brand-new network (N:) device.
Implements Bluetooth, NTP, text-to-speech.
RepRap is an open-source (hardware, software, and documentation) desktop fabrication system which lets you construct arbitrary objects (or parts for assembling more complex systems). It's unique in that you can construct one yourself for about $400us, and it is fully capable of making duplicates of itself.
An open source DIY robotics/rapid prototyping kit much like an Erector set. Lots of standardized pre-milled bars, rods, connectors, and components. Build your own plotter, CNC machine, RepRap, scanner table, or what have you. Capable of three axes of linear motion. Comes with all the electronics you need, including an Arduino, stepper motors, and a motor driver board.