USB Composite library for STM32F1 (HID, Serial, MIDI and XBox360 controller)
A Firmware-Only USB implementation for Atmel's AVR Microcontrollers
The R2Duino is a fully assembled USB stick sized Arduino clone based on the ATmega328P. It has the same functionality as the Arduino Nano 3.0, but comes in a different package.
You can now add shield PCBs, shield kits, and extra Digisparks to your order - click here for all the details!
StickDuino - USB Stick Sized Arduino Clone