Lichen Resources
General References
Purvis, William. 2000. Lichens. Washington, D.C.: Smithsonian Institution Press in association with the Natural History Museum, London. This book has beautiful photographs, and it is packed with all the most interesting aspects of lichen biology. I can't recommend it highly enough.
Lichens of North America is both a book (see Brodo below) and a website. The website has many great photographs as well as unusual information on lichens such as how animals and people use them.
Lichen Land, hosted by Oregon State University, has introductory lichen information and an online synoptic key for lichens of the Pacific Northwest.
Printed Keys
Some helpful printed keys are described below. For many people, learning how to identify lichens requires more than good keys, it requires mentorship. The California Lichen Society periodically sponsors congenial lichen identification workshops in the San Francisco Bay Area.
Brodo, Irwin M. 2001. Lichens of North America. New Haven: Yale University Press. This is a large books with excellent photography. Since it tries to cover all of North America, the keys are quite long and include many species that are never found in California, much less Santa Cruz County. It is available in Museum of Natural History Collections as well as the Reference section of the Science and Engineering Library.
Hale, Mason E., and Mariette Cole. 1988. Lichens of California. Berkeley: University of California Press. This book has no color photographs, but they keys are shorter than Brodo.
Herre, Albert W. 1910. The lichen flora of the Santa Cruz Peninsula, California. Baltimore, Md.: Washington Academy of Sciences. This is one of the few regional lichen floras ever published for North America. Herre was an icthyologist but did not get along with someone in the zoology department at Stanford when he was in graduate school. He wrote his dissertation on lichens instead. This publication has outdated names and no figures, but the location descriptions can be quite detailed. Available in the reference section of the Science and Engineering Library.
McCune, Bruce, and Linda Geiser. 1997. Macrolichens of the Pacific Northwest. Corvallis: Oregon State University Press. This books has color photos, relatively short keys, but it does not cover crustose lichens.
Lichen Photography
I really enjoy the photos by Einar Timdall: http://www.toyen.uio.no/botanisk/lav/Photo_Gallery/PG_index.html.