I can assist you partially as the resources I have known are the paid ones.
But they are alike the real SAT tests. College Board didn't officially release the Subject Test sample papers, but they released the practice papers in the form of practice books.
A prep company called the video solutions of SAT Subject Tests (PCM) and they are available on their site.
You can [url=http://]buy online SAT Subject Test series[/url] here.