General
Avocadosource: A website containing thoughts and ideas about avocado culture. Has articles posted on topics related to avocado culture.
California Avocado Commission: A wide variety of information about avocados
California Avocado Society: Information on all aspects of growing and marketing avocados.
UC Davis ANR Communications: Source of publications, some of which cover avocados.
UC Food Safety: University of California food safety program
Home Avocado Information: From Texas Agricultural Extension Service, Texas A&M University
Postharvest Research: University of California postharvest research and information. Includes information on avocados.
Tropical Research and Education Center: University of Florida. Source of books and publications, some of which deal with avocados.
University of Florida: How to get University of Florida Publications (do search using keyword of "avocado").
Ventura Cooperative Extension: Avocado, Minor Subtropicals, and Soils/Water - Ben Faber covers issues of soil management by way of fertilizer, irrigation, and erosion control. In tree crops he works primarily in avocado, cherimoya, litchi, and longan and in citrus.
Agriculture Law: Website dedicated to providing farmers and ranchers with the most complete source of information on agriculture policy.
Avocado Varieties
California Rare Fruit Growers Organization: More than just avocados
Fruit and Nut Research & Information Center at the University of California, Davis
Persea Image Collection Photographs of avocado varieties in the Persea collection maintained by the National Plant Germplasm System, U.S. Dept. of Agriculture, Agriculture Research Service.
Irrigation
CIMIS: Link to California Department of Water Resources
CIMIS calculator: Link to the California Avocado Commission CIMIS calculator
Irrigation Water Salinity and Crop Production: a free document in PDF format
USDA Salinity Lab: The section on frequently asked questions is quite good
Pests
Avocado Pests and Diseases: Link to the IPM page at UC Davis
Diseases of Avocados: University of Florida document
Persea Mite web page about persea mite and other pests, by Mark Hoddle
Subtropical Fruit News
Download Page: Archive issues of the Cooperative Extension "Subtropical Fruit News" with articles on avocados, citrus and other subtropical fruit crops.