Here at the Cryogenics and Fluids Branch of Goddard, we concentrate on ways to cool spacecraft. Although the apparatus we use for spacecraft is specialized, some of the general approaches are the same as used in everyday life. To point out the similarities, I've made a short table of cooling comparisons. One interesting feature of materials at low temperatures is that the air condenses into a liquid. The two main gases in air are oxygen and nitrogen.
Liquid nitrogen is used as a coolant.
Helium, which is much rarer than oxygen or nitrogen, is also used as a coolant. We have an introduction to ADR's. For info, see the Introduction to XRS . There is a field devoted to freezing people, called cryonics. It's currently used for freezing people who die of diseases that, they hope, will be curable by the time scientists learn how to revive people.