the cook's thesaurus
I just HAVE to share this link!
"The Cook's Thesaurus is a cooking encyclopedia that covers thousands of ingredients and kitchen tools. Entries include pictures, descriptions, synonyms, pronunciations, and suggested substitutions." (http://www.foodsubs.com/)
Returning for a moment to the flour discussion . . . I found this incredible page on the site with detailed substitutions for all-purpose flour in both general baking and yeast bread recipes. But there's so much more.
If you have time this weekend, check it out!