Can I store dry ingredients (flour, baking powder, baking soda, etc) together? I am planning on making a bunch of gingerbread this year, the recipe I use takes both baking powder and baking soda.  In order to cut down on dishes and time I thought I might mix all of the dry ingredients together in multiple batches and store it in the fridge for a week or two until I have time to actually bake it. 

Can anyone tell me if it will cause problems to store baking powder and baking soda (and the rest of the ingredients) mixed together for couple of weeks in the fridge?
As long as they're all dry ingredients, then you should be just fine — after all, that's exactly what a box of packaged cake mix is.

Again, if it's just dry ingredients, I see no need to refrigerate it. I would put it in an airtight container — preferably a glass jar*. Placed in your pantry, it should have a shelf-life of a least a couple of months.

&#42; Glass jars are my preference for storing dry ingredients — they're easy sanitize, and the twist-off cover makes an airtight seal: