In California, there is one website that nearly every school district uses to advertise jobs. That site is: http://www.edjoin.org/. If there is a school job in the state, it will be there.
There is also a site for community college jobs. https://www.cccregistry.org/jobs/searchForm.aspx. These are site for all teaching jobs, and you will have to narrow your search.
In California, one will be probably not be able to teach only psychology—we often have to add other social science classes to our schedules (I've also taught US Government, Sociology, and World Religions here). It has to do with graduation requirements and the culture in the past 20 years or so. Also, many electives in Cali are being cut as a result of the budget issues at the state level.
Here is where we really need your expertise--especially for those of you not in California. Since this blog is about teaching high school psychology, I suspect most of us will be at the high school or community college level. I'm not aware of any centralized location to seek out psych teaching jobs at the high school level across the US.
I recall that making contacts at the AP reading was a great place to find out what was available. I vaguely remember how counties in Illinois had listings for their areas. I can thank the Psych-News listserv for finding out about my current job.
What is out there now? If your state has such a web site(s) or services, please add the information and any insights in the comments section. Thanks in advance for your contributions.