References:
+ various relevant circuit fragments:
http://www.ladyada.net/learn/sensors/cds.html
http://klk64.com/arduino-spi/
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1264143673
+
+ pcb layout in gEDA of an Arduino shield:
+ http://lowvoltagelabs.com/products/videooverlayshield/