What is a good substitute for dry white wine?

Dry white vermouth - for all the reasons mentioned above, and also because it's economical - a bottle of Martini & Rossi or Noilly Pratt typically costs under $10, and goes a long way.

I echo the dry white vermouth suggestion, especially because if you don't also
drink white wine, it takes up fridge space!

Martini and Rossi white vermouth. I've used it for years without fail.

Julia Child always advocated dry white vermouth (French, please!) even instead of white wine, as it's an easier substance to keep on hand.

Dry vermouth may used in sauces. I've used it several times and the sauces were perfect

Depends what you are making. For deglazing a pan, making a sauce, doing a risotto, and similar savory activities, you could substitute chicken or vegetable stock or, for that matter, just plain water.