BugGuide - an incredible site where users can post pictures of unidentified "bugs" as well as browse through guide pages filled with text and thousands of pictures
Checklist of the Collembola of the World - a site devoted to Collembola that is filled with information, maps, and photos of thousands of Collembola species
Tracks and Sign of Insects and Other Invertebrates: A Guide to North American Species by Charley Eiseman and Noah Charney.
Life in the Soil: A Guide for Naturalist and Gardeners by James B. Nardi
