- L.A. Burial Permits, 1870-1892
- CA Death Index, Pre-1905 (Partial)
- CA Death Index, 1905-1939 (Must register, but it's free)
- CA Death Index, 1940-1997
- Social Security Death Index
- Southern California Obituary Resources Project
- O.C. Cemetery Info
- RootsWeb (Free genealogy resources)
HeritageQuest (available through many libraries) also contains a lot of useful information, and Ancestry.com is even better, but charges a membership fee.
Of course, to get very far with historical research you'll probably need to talk to people, read actual books, and dig through the extant records and newspapers yourself - But you can get a good jump start with sites like the ones listed above.