For those of you still using the Atari 1050 disk drives for your 800/XL/EX computer, the people at Whizzo software have made open source the hardware and Arduino sketch required to build a disk drive emulator. If you don't remember what an Atari 800 was ...
(image - oldcomputers.net)
Unfortunately I only had access to a 400 at the time, with that membrane keyboard... But I digress. Using an Arduino Uno or Mega2560-compatible board and a microSD card shield, you can now use that hardware to load disk images for the aforementioned systems. For more information, including the wiring details and Arduino sketch, visit the Whizzo software webpage.
If you are going to move forward with this project, consider our Freetronics EtherTen or EtherMega boards - the Arduino Uno and Mega2560-compatibles with onboard microSD socket, Ethernet and optional PoE support.