The Adafruit Standalone AVR ISP Programmer Shield Kit is a bit of a niche product. It converts an Arduino into an AVR in-system programmer that doesn't require a PC to supply the target hex image. I added some improvements to the firmware: it no longer has the 2x space overhead for ASCII hex files, instead working with pure binary; it fixes a bug with certain kinds of hex files; and it has better sounds to report success and failure.
I've been hacking pretty hard on these Christmas lights lately. Here's my GitHub repository, which several people have reported they're using happily on their own homes. My own installation is based on a Teensy that I've updated with the Arduino Leonardo bootloader. I'm running two strings directly from a USB power source (an old Kodak Zi8 wall adapter). My G35Arduino library is able to synchronize multiple strings of lights, and that's what I'm doing on my house. I'll post videos later.
