Here is a list of what I have found over time when you don’t have something.
Brown Sugar – 1 tbsp or so of molasses per cup of regular sugar. Get it to mix thoroughly.
Bread Crumbs – Rice, quinoa, fresh bread, toasted bread, panko, and one of my favorites, croutons.
Flour – When a recipe calls for a specific type of flour, you generally can use all-purpose flour. Might need to do a little web searching to see what someone else has done and adapt accordingly.
Herbs – We have run out of some herbs every now and then. Sometimes it will call for something that you just finished up at lunch. If you know how they smell and taste, find one that is fairly close, most often you will barely notice the difference. Other times, it will change the flavor. If it fails, you now know what not to do next time, if not, well, you now have a new variation to work with in the future.
Buttermilk – not everyone keeps this in their fridge. We don’t. Just add lemon juice from that funky yellow bottle. Roughly a tablespoon per cup will work.
Rice Flour – haven’t tried this yet, but I kind of figured it would be something like this. http://www.instructables.com/id/DIY-How-to-Make-Rice-Flour/
If you have anything you would like added, leave a comment and I will add it here.