uno2tap
uno2tap lets you use an Arduino Uno in place of a C64 datassette. C64 tape images may be streamed from a PC over USB to the Arduino. The tap server software is written in Java so this will work on various platforms.
See the README for more info.
This was inspired by uno2iec which uses an Arduino to emulate a 1541 floppy drive.
Nicola Fossati has extended this with a gui and motor control: uno2tapGui