AJR Newslink lists dozens of California newspapers.
Newspaper Archives on the Web: Organized by state, this site provides information on holdings and fees, with links to the papers and their archive sites.
Los Angeles Times: Links to topics in current issue as well as a link to its archives (fee required for full text of stories).
The Sacramento Bee: Links to topics in the current issue, with for-fee searching of its archives back to 1990.
San Jose Mercury New: San Jose's leading newspaper. Searchable archive from 1985 to the present (full-text retrieval with registration). The Merc also features a searchable archive of 44 other papers, with a fee for full-text retrieval.