Skeleton

The calcium carbonate or silica spicules of most sponge genera make them too rough for most uses, but two genera, Hippospongia and Spongia, have soft, entirely fibrous skeletons. Early Europeans used soft sponges for many purposes including padding for helmets, portable drinking utensils and municipal water filters. Until the invention of synthetic sponges, they were used as cleaning tools, applicators for paints and ceramic glazes and discreet contraceptives. However by the mid-20th century, over-fishing brought both the animals and the industry close to extinction.

Many objects with sponge-like textures are now made of substances not derived from poriferans. Synthetic "sponges" include: personal and household cleaning tools; breast implants, contraceptive sponges.
The luffa "sponge", also spelled loofah, which is commonly sold for use in the kitchen or the shower, is not derived from an animal but from the fibrous "skeleton" of a gourd (Cucurbitaceae).