SPI Blink tutorial

I've been trying to learn SPI as it relates to Arduino. I've managed to control an LED using a digital potentiometer courtesy of a youtube tutorial but I'm more interested in controlling one Arduino with another using SPI. I understand that it requires code on both ends but I have no idea how to make a slave Arduino accept data from a master via SPI.

Are there any hints out there or basic tutorials for making pin 13 of a slave Arduino blink? Thank you very much and have a great day!

http://forum.arduino.cc/index.php?topic=120049.0

And for more references: https://www.google.com/#q=connect+two+arduino+spi

Try Nick Gammon's page also for uC to uC comm's. http://www.gammon.com.au/forum/?id=10892