I belong to 3 different county psych associations in the area I'm looking for jobs, and so far, there haven't been many jobs posted in the listservs at all (maybe 2 out of the 40+ postings I've seen), moreso ethical questions, lectures/events/workshops, and requests for referrals for clients with a special issue. The listserv from your graduate school is a better resource for actual job postings than other associations you are consider joining, at least that's how it's been for me.
Listservs can be public or private, and the private ones are ones you typically have to pay to belong to (county psych associations, state psych association, professional psych associations such as psychoanalytic societies). It's hit or miss as to whether any of them will post job listings, but you can always ask the member board before if that's something they provide before you join and pay the fees.
You could try APPICs post-doc listserv that's free to join. Keep in mind these will be national positions..all over, not just in one state.
https://www.appic.org/E-Mail-Lists/Choose-a-discussion-list/Postdoc-Network
Also, the next big wave of APPIC postdocs is about to hit later this fall, so if you check around the site, they'll list sites that you have to apply through appic for the 2016-2017 year (deadlines typically November-January). Positions in Counseling Centers (PICC) also lists open positions specifically at counseling centers if you check that site.
Finding a job/position to accrue postdoc hours depends on what state you live in and the licensing requirements, and where you hope to work, as well as how competitive the area is. You could try applying for therapist jobs in any setting as long as they're willing to take on a postdoc and provide the required supervision, which would mean you'd need to contact the site directly to inquire. I"m still using craigslist, Indeed.com, and linkedin to look for jobs, as well as specific community mental health organizations' websites to apply for jobs.
Others have opted to work with psychologists who are private practitioners, but you have to have the connections to know who'd be willing to take on postdocs in their practice.
I suspect we're in the same boat since you're in CA! I posted a similar question here:
http://forums.studentdoctor.net/thr...sychological-assistant-postdoc-in-ca.1160212/
Someone back in 2012 suggested joining county psych associations (paying the fees) and posting a message on their listservs asking if any practitioner is taking on any psych assistants, and I have not had any luck yet, but I've posted on 3 listservs so far with that request. I've done a little cold contacting of psychologists with a cover letter and CV, posting on listservs, and applying to jobs so far. I'll let you know which one of those methods ends up working out for me.
Good luck!