Dryer sheets: These are unnecessary. Most clothes don't get staticky if you don't let them tumble around in the dryer for too long. If you do get a few staticky items, you can discharge the electricity by snapping them vigorously in the air. This is particularly exciting on dry days in the winter.
Baking powder: Some of us are uncomfortable consuming aluminum. Aluminum-free baking powder is expensive. Baking soda and cream of tartar are often touted as a less-expensive substitute, but cream of tartar is hard to find in bulk and still fairly pricey.
The purpose of baking powder is to create an acid and base reaction in the middle of your food so that it will bubble up and then be trapped by cooking. Well, what's the classic kitchen acid-and-base combination? Baking soda and vinegar, of course! And vinegar is very cheap and very easy to find in bulk.
The trick is figuring out the right proportions. Right now I'm using about 1/2 tsp. soda to 2 Tbs. vinegar as a substitute for 1 1/2 teaspoons of baking powder. If the substance contains some acidic ingredients (like fruits or veggies) or very strongly flavored ingredients (like chocolate) not quite so much vinegar might be needed. But knowing the dire consequences of unreacted soda, I generally err on the side of caution.