University of California
Ucmp: Porifera
Detailed site, lots of pictures, and easy to understand descriptions of the phylum known as Porifera. This one is a winner!
University of California
Ucmp: Phylum Porifera
Click on the name of the class of sponge you want to know about, and you'll see a picture and a description of it.
Tree of Life Project
The Tree of Life Web Project: Animals
Extensive site that contains much information about the various animal phyla. Each phyla gives photos, common examples, scientific names and references. Collection of 1630 websites about bio-diversity.
Wikimedia
Wikipedia: Sponge
Wikipedia offers detailed information on sponges, or poriferans, animals of the phylum Porifera.
Other
Sponges, Phylum Porifera
Discusses sponges that may be kept in salt-water aquariums, along with what they need to live. Good general information.
Other
Kids' Cruz: Taxonomy
Kidzcruz.com provides a list of phylums in the animal Kingdom. Both Latin and English names are included.
Encyclopedia of Life
Encyclopedia of Life: Sponges
The Encyclopedia of Life presents this in-depth overview of Sponges (Porifera), including their habitats, size, conservation status, and much more. Images of this phylum and maps of its global distribution can also be found here.