Diatomaceous earth for fleas and worms. Haven't tried it myself yet but have read great things and have a few people willing to split a 50 pound bag of the stuff, so that's going to be this week's job.
'brown listerine' or it's generic is good for hot spots, ear issues, general wound care
canned pumpkin, slippery elm for digestive issues
a mix of yeast infection cream and cortisone cream for ear infections/hot spots
Many of the horse supplements for joints can be used for dogs too, I've got a tub of a joint mix that works great and is a fraction of the cost of the canine or human version. I learned that years ago when I went into a store and noticed that the human, dog and horse stuff were all in the same place, but the human ones were more than the dog ones but seemed the same otherwise (different label, same amount) and then the horse stuff was ten times the size and only double the price. Called the company and they confirmed it was all the same, just in bulk for horses. You have to double check with products and of course calculate the dosage but it's much less cost wise (I keep a small amount out to use, the rest in the tub in the freezer).