Thanks for this thread and its resources!
I was happy to find out about this free resource today, which was released from Midwest Permaculture in April, 2013.
Because...it lays out an oak guild, and it's being provided by a permaculture center in the midwest (my region)!
It's called:
Midwest Permaculture Presents:
Plant Guilds
By Bryce Ruddock Illustrated by Jesse Tinges Forward by Becky Wilson Editing and Layout by Milton Dixon
http://midwestpermaculture.com/2013/04/plant-guilds
I found the oak guild really helpful, with plants that I know are suited to my climate (great lakes / midwest / zone 5b/6a).
It also has many other plant guilds.
Here's a list of what's included:
----------------------------------------
Ash Guild
Bee Guild
Evergreen Guild
Fruit Tree Guild
Oak Tree Guild
Service Tree Guild (serviceberry aka juneberry aka saskatoon, etc.)
Tree Hazel Guild
Walnut Guild
Wet Meadow Guild
Appx - Spring bulbs, nurseries, rootstocks
Mariamne