It's no secret that we're a little bit in love with the sn3218 PWM LED driver. It's found its way onto the PiGlow, the Display-o-Tron, some other super secret sauce, and now this 18-Channel, 8-bit PWM LED Driver.
This beauty will work with either the Raspberry Pi, and yes it'll work fine with any existing PiGlow code, although the results might be a little weird, or with Arduino boards and even the Trinket/Gemma thanks to a little TinyWire magic in the library.
You can basically use this to build a D.I.Y. PiGlow with any layout you want- a Christmas tree might not be a bad idea right now!
Find it here: http://shop.pimoroni.com/products/18-channel-8-bit-pwm-led-driver-w-i2c-interface
Find the library here: https://github.com/pimoroni/pimoroni_arduino_sn3218
I've also been playing with tiny little micro gear-motors and this board, and I suspect it might do interesting things with piezos too. We'll see!