Nurseries and Gardens with plant databases, lists of plants for native gardens, most with photos (some are not exclusively devoted to CA native plants)

El Nativo, http://www.elnativogrowers.com/Natives.htm
Las Pilitas Nursery, http://www.mynativeplants.com/
Monterey Bay Nursery, Inc.: http://www.montereybaynsy.com/A.htm
Mountain States Wholesale Nursery, http://www.mswn.com/
Native Sons, http://www.nativeson.com/
Rancho Santa Ana Botanic Garden, http://www.rsabg.org/
San Marcos Growers, http://www.smgrowers.com/info/images.asp
Saratoga Horticultural Research Foundation, http://www.stanford.edu/~rawlings/SHRF/SHRF.htm , plant culture data sheets, no photos but good information.
Suncrest Nurseries, http://www.suncrestnurseries.com/ (no photos)
Theodore Payne Foundation, http://www.theodorepayne.org/
Tree of Life Nursery, http://www.treeoflifenursery.com/,  http://www.californianativeplants.com/

Photo collections/databases
CalFlora, database of native plant photos, http://www.calflora.org
California Academy of Sciences, California Wildflowers, http://www.calacademy.org/research/botany/wildflow/
California Gardens, http://www.californiagardens.com/Lists/native.htm
California Native Plant Link Exchange, database with links to photos, info, http://www.cnplx.info/index.html
California Native Plant Society, http://www.cnps.org/
Cal Photos, database of native plant photos, http://calphotos.berkeley.edu/flora/
County of Los Angeles Fire Department, Forestry Division, Plant ID, http://www.lacofd.org/Forestry_folder/LFM/Plant ID Guide 2002 web.pdf
Field Guide to the San Gabriel Mountains: Natural History: Plants, http://tchester.org/sgm/plants/
Jepson Floral Project, Jepson Online Interchange, http://ucjeps.berkeley.edu/interchange.html
Jepson Horticultural Database, http://ucjeps.berkeley.edu/interchange/hort_form.html
LA Dept. of Public Works, Los Angeles River Master Plan Landscaping Guidelines and Plant Palettes, (plant lists start on pg. 124) http://ladpw.org/wmd/watershed/LA/LAR_planting_guidelines_webversion.pdf
Los Angeles/San Gabriel Rivers Watershed Council, The Plant Profiler, http://theplantprofiler.com/
Metropolitan Water District of Southern California, Heritage Garden Guide, http://www.bewaterwise.com/
National Resources Conservation Service, PLANTS National Database, http://plants.usda.gov/
Nature At Hand, http://www.natureathand.com/
Southern California Wildflowers and Other Plants, http://www.calflora.net/bloomingplants/index.html
Virginia Tech, Forest Biology and Dendrology, http://www.cnr.vt.edu/dendro/dendrology/factsheets.cfm
Wildflowers of the Santa Monica and beyond, http://www.timetotrack.com/jay/
Wildflowers of the Santa Monica National Recreation Area, http://www.researchlearningcenter.com/bloom/bloom.htm#Names
Wildflowers of Southern California, A Photographic Gallery, Barbara J. Collins, http://www.callutheran.edu/wf/
Wildscaping, http://www.wildscaping.com/plants/plantprofiles.htm

Google image search of plant