[The above was meant to be posted here...as an answer]:
The California Attorney General's Office maintains an online list of
all registered charities in the state, which can be searched here:
Entering Oakland in the "City" text box, yields the following:
"There are 2083 Matching Records"
followed by the actual list of the non-profit organizations (listed
25 to a page). Many of the organizations include a link, "On-Line
Financial Records Are Available", in case you want some additional
information about the groups.
The main search page also includes a link:
"For an overview of the information contained in this database and how
to understand it, Click Here"
By clicking on the text, you'll be taken to additional information
about the list itself, should you so desire.
Before rating this answer, please let me know if you require any
additional information. Just post a Request for Clarification, and
let me know how I can help.
search strategy: Used bookmarked sites for California non-profit organizations.