AVR-CDC is a pure SW based USB-RS232C interface using the CDC (Communication Device Class) protocol. Although the bulk endpoint required for CDC is not allowed within the low-speed USB standard, it works fine on major platforms.

An evolution of the homebrew MP3 player - if you are interested in building your own, here is all you need.

Open source USB sensor box

MCU based infrared repeater allow to control an A/V equipment that is behind a wall.

MIDI, or Musical Instrument Digital Interface, is a specification for a communications protocol between digital synthesizers and other digital music devices. It was developed to be as simple and general as possible, to give synthesizer manufacturers as much flexibility as possible, yet still have their instruments talk to each other without communication problems. Here is a simple circuit for MIDI output that works well with Wiring or Arduino, the PIC microcontrollers, the BS-2, and the BASIC ATOM Pro24.

The AES block cipher on AVR controllers

Amforth is a compact forth interpreter and compiler for the atmel avr atmega microcontroller family which is implemented in assembly language and amforth itself. It is an interactive system running completly on the controller. It does not need additional hardware beyond a power supply.

An AVR-based small test application which implements read and write support for MMC, SD and SDHC cards.

The idea for a 1-key keyboard comes from the need as an interaction designer to make “cheap, quick and dirty prototypes.” When creating a quick screen-based demo in e.g. Adobe Flash, a common way of quickly prototyping physical actions is to assign actions to certain key presses on a keyboard.

Dallas Semiconductor (Maxim) produces a family of devices that are controlled through a proprietary 1-wire interface. On a 1-wire network, a single "master" device communicates with one or more 1-wire "slave" devices over a single data line, which can also be used to provide power to the slave devices. How to connect such devices to Arduino?