University of California
Earthworm Information
A very detailed look at how earthworms affect the world around them. It also has a section which explains how earthworms deal with certain scenarios and materials like fertilizers. Lastly, physical descriptions are given to help one...
BBC
Bbc: Nature Wildfacts: Common Earthworm
Before you go looking for an earthworm, learn more about it from this detailed fact sheet and from these close-up photos.
Other
Earthworm Behaviour and Habitat
This resource focuses on where different species of earthworm like to live.