Use:

By dolphins:

In 1997, use of sponges as a tool was described in Bottlenose Dolphins in Shark Bay. A dolphin will attach a marine sponge to its rostrum, which is presumably then used to protect it when searching for food in the sandy sea bottom. The behaviour, known as sponging, has only been observed in this bay, and is almost exclusively shown by females. This is the only known case of tool use in marine mammals outside of Sea Otters. An elaborate study in 2005 showed that mothers most likely teach the behaviour to their daughters.

By humans:

Skeleton as absorbent:

In common usage, the term sponge is applied to the skeleton of the animal, from which the tissue has been removed by maceration and washing, leaving just the spongin scaffolding. Calcareous and siliceous sponges are too harsh for similar use. Commercial sponges are derived from various species and come in many grades, from fine soft "lamb's wool" sponges to the coarse grades used for washing cars.

The manufacture of rubber-, plastic- and cellulose-based synthetic sponges has significantly reduced the commercial sponge fishing industry in recent years.

The luffa "sponge", also spelled loofah, commonly sold for use in the kitchen or the shower, is not derived from an animal sponge, but from the locules of a gourd (Cucurbitaceae).

Antibiotic compounds:

Sponges have medicinal potential due to the presence of antimicrobial compounds in either the sponge itself or their microbial symbionts.