USB control panel with endless turn knobs
Options for the Arduino you have:


Get an Arduino supporting HID drivers (e.g. 32u4 based boards, Due /Zero/ Arduino Leonardo/ Micro or Pro Micro/ M0)
You use this library it supports UNO/MEGA/Leonardo/(Pro)Micro/ any 8u2/16u2/at90usb8/162/32u2/32u4 compatible boards and some more


Then you have to "just" code the communication between your programm and the HID driver -> pretty standard serial/usb stuff.
The parts (knobs) you seek could be rotary encoders, which have no fixed zero point, endless rotation and need 2 input pins per encoder (except GND or optional push function). The signals a rotary encoder produces (and what can be handled by libraries) are based on a 2-bit gray code available on 2 digital data signal lines. 
So when choosing whatever Arduino make sure you have enough (usable) I/O ports for the number of encoders and possible additional parts (status led/s or similar, I2C LCD display)