Luigi Di Fraia well known for his digital replacement of the datassette (DC2N) has been working on a new project. This time he is working on a USB system for the Commodore C64. The prototype uses two devices. A cartridge to provide software and commands to operate the USB device, and a user-port device that interfaces with the USB stick. With the proto-type it is possible to transfer files at 1.2 kB/s (serial) or 9.5 kB/s parallel. You can follow the progress of USB-64 on Luigi's web page.