Insects, Arachnids, and Arthropods
California Beetle Project - a database of 50,000 CA beetle records, a photo gallery, and lots of other related info. Sponsored by the Santa Barbara Museum of Natural History. Also have numerous other collections at the museum and research going on.
California Dragon and Damsleflies - downloadable dragonfly field guide, images and descriptions, event info, CA species checklist, and CA sightings info. (scroll to bottom of page, after book sales info)
Insects.org - their "Entophiles" are a wealth of knowledge with photos and descriptions, a Cultural Entomology Digest, a "Bug of the Week", and more!
Pollinators.org - info on the natural history of honey bees and challenges they are facing. Plus many links on beekeeping.
Spider Research - From the Entomology Department at the University of California, Riverside