I'm in the middle of a small microcontroller device that allows one to bypass the need for a computer to run a CNC.

Features
-SD card reader
-RS232 port
-LCD display

Operation:
-You put the CNC in DNC mode
-You select the file off the SD card and it drip feeds the program over RS-232

Benefits:
-any size program, not limited by CNC memory
-no external computer required
-easy transfer of gcode from one computer to CNC
-possibility to be integrated with the auto tool zeroing board I made (select what tools you want to zero and the board does it automatically)

Cost is to be determined but I'm thinking it'll be in the $250 range depending how much demand there is for it. The more demand the cheaper the boards are so if you have an interest in this device, send me a PM.

It's a lot cheaper than an upgrade to the USB drive, floppy drive or harddrive from the manufacturer. Sure you could do the same with a cheap laptop with a SD reader running a DNC drip feed program but it'll still probably cost more than $250.