[bonzini]

Decimeter is used occasionally for densities, because 1 g/cm^3 is the same as 1 kg/dm^3 but the latter is a little easier to imagine. The cube decimeter is also used under the name of... liter.

Likewise, there is also deca- and hecto-. Hectograms are used for shopping.

Decameter (dam, 10 m) is never used, but there is a non-SI unit of area based on it, called the are. Nobody uses the are, but its multiple the hectare (1 square hectometer) is common in some countries when talking about land plots. It's a little less than 2.5 acres, for people in the US.