Ladyada and pt had an old NeXT keyboard with a strong desire to get it running on a modern computer. These keyboards are durable, super clicky, and very satisfying to use! We spent a few days and with a little research we got it working perfectly using an Arduino Micro as the go between. Now this lovely black deck works like any other USB keyboard. Sure it weighs more than our Macbook, but its worth it!
Your microcontroller probably has an ADC (analog -> digital converter) but does it have a DAC (digital -> analog converter)??? Now it can! This breakout board features the easy-to-use MCP4725 12-bit DAC. Control it via I2C and send it the value you want it to output, and the VOUT pin will have it. Great for audio / analog projects, such as when you can't use PWM but need a sine wave or adjustable bias point.