It's impossible to pick just three! Earth is full of natural mixtures, but here are three common examples from different categories:

1. Air: A mixture of gases, primarily nitrogen and oxygen, but also containing argon, carbon dioxide, and trace amounts of other gases.

2. Seawater: A mixture of water, dissolved salts (like sodium chloride), and other substances like minerals and dissolved gases.

3. Soil: A mixture of minerals (weathered rock), organic matter (decomposed plants and animals), air, and water.

There are countless other examples like sand, granite, blood, and even the human body!