The most common one you run into is carbonated soda. In a closed can of soda, the solution is saturated with carbon dioxide because the atmosphere inside the can is mostly carbon dioxide. When you open the can, the pressure of carbon dioxide decreases, drastically lowering the solubility of carbon dioxide. The resulting soda, then, is a supersaturated solution, which gives off the excess carbon dioxide as bubbles over time.
Some chemical heat packs also use supersaturated sodium acetate . When a small disc is manipulated in them, the solution is disrupted enough that the sodium acetate crystallizes, giving off energy.
