Just announced on Slashdot, a new Pi distro from Adafruit, Occidentalis v0.1, which is a Raspbian customized for hardware hacking:
And direct from the horse's mouth:
Overview: http://learn.adafruit.com/adafruit-raspberry-pi-educational-linux-distro/
Download: http://learn.adafruit.com/adafruit-raspberry-pi-educational-linux-distro/occidentalis-v0-dot-1
It'll be interesting to see where this goes. Adafruit are such an excellent outfit, and very responsive to feedback.
Although this is just a small tweak on top of Raspbian (for now), Adafruit's hardware focus could take this to interesting places, and it's quite likely to make life easier for non-experts who wish to interface Adafruit's products to the board.
Morgaine.