Ranchos!
http://www.lib.berkeley.edu/EART/rancho.html

http://www.vcnet.com/sbra/projects/camulos/significance.html

http://www.ccnet.com/~laplaza/calhist.htm

http://www.toucanvalley.com/ranchosfc.htm

http://www.myrong.com/California%20Rancho%20Sites.htm

http://www.geocities.com/cott1388/notes.html

http://www.zorro.com/zhistory.htm

Vacqueros!
http://www.homestead.com/vaquerodays/history.html
http://windyjoe.homestead.com/cowboy.html
Almost everything there is to say about cattle roundups (rodeos) in the 1840s: http://freepages.genealogy.rootsweb.com/~crow2000/california_trail_herd_intro.htm 

Roundups and Rodeos
http://www.carodeo.com/history.htm
http://www.cattleclub.com/
http://www.ci.san-bernardino.ca.us/site/htm/history.htm
Incredible "Rancho" site. You can even draw your own cattle brand and name your own ranch! http://www.nhm.org/education/cahistory/brand/

http://www.laokay.com/halac/Introduction.htm

http://www.lib.berkeley.edu/EART/tour/rancho/
http://www.geog.ucsb.edu/~joel/g148_f04/lecture_notes/rancho_period/sespe_diseno.jpg
http://www.geog.ucsb.edu/~joel/g148_f04/lecture_notes/rancho_period/rancho_map1.jpg

Mexican California
http://www.ohp.parks.ca.gov/5Views/5views5b.htm
http://www.pbs.org/weekendexplorer/california/sandiego/lajolla_heritage.htm

Spanish and Mexican Land Grants in California--An index of original disenos! There should be a way to use the ID numbers to view the disenos, but I haven't found it yet. Let me know if you find it! http://www.ss.ca.gov/archives/level3_ussg3.html

Mexican War Information
(plus other goodies from Museum of the City of San Francisco)
http://www.sfmuseum.org/hist6/muzzey.html

http://www.ohp.parks.ca.gov/5Views/5views5b.htm

http://www.pbs.org/weekendexplorer/california/sandiego/lajolla_heritage.htm

Overland Trails to  California

Primary Sources of Overland Travel to California http://memory.loc.gov/learn/features/timeline/expref/oregtral/oregont.html

Autry Mini Lesson on Hide & Tallow Trade