I recently bought the Margaret Fulton Encyclopedia of Cooking. It is an amazing cook book (and I only paid $10).
I am one of those people that has trouble menu planning. So I get to the end of the week and I have bits of bobs in the fridge. One week I had tomatoes and some eggs. I looked up Tomatoes and found a great recipe for a tomato and egg Gratin.
I currently have 3 big punnets of natural yogurt in the fridge (don't know why) so I have found a receipt for a yogurt soup and a Chicken Dish which uses yogurt as the marinade.
She really is a cooking legend.