The PiGlow is a small board for the Raspberry Pi that adds 18 single colour LEDs. Each can be controlled through I2C over the GPIO header, and you can even dim LEDs.
node-piglow (GitHub: zaphod1984 / node-piglow, License: MIT, npm: piglow) by Manuel Ernst is a module for talking to the PiGlow. It uses i2c and allows you to address the LEDs like this:
piGlow.l_0_0 = 100; // lights up the first LED in the first LEG with a brightness of 100 piGlow.l_0_0; // lights up the first LED of the first LEG with maximum brightness (255) piGlow.leg_0 = 100; // lights up the first leg (8 consecutive LEDs) with brightness of 100 piGLow.leg_0; // maximum brightness for the first leg piGlow.ring_0 = 100; // sets LED 1 of leg 1, LED 1 of leg 2 and LED 1 of leg 3 to 100 iGlow.ring_0; // sets LED 1 of leg 1, LED 1 of leg 1 and LED 1 of leg 2 to 255
Manuel made node-piglow-load with it which uses the PiGlow to visualise system load. Since the API is very simple you could hook it up to lots of other interesting things, perhaps build status from your next big Node project. I've had my eye on the PiGlow for a few weeks for fun little hardware projects so I think node-piglow might make me get my wallet out.