Plant selection
The Butterfly Net: Lepidoptera Conservation Tool (beta)
National Wildlife Federation : Keystone Plants by Ecoregion: Mediterranean California
Las Pilitas: Plants for Southern Oak Woodland
Santa Monica Mountains Fund: Monarchs and Milkweed
Plant identification
University of California Statewide Integrated Pest Management Program Weed Photo Gallery
UC Davis Weed Identification Tool
Common Weed Seedlings of Central California Vineyards (a great weed seedling identification guide prepared for Central California, but applicable to Southern California)
Videos