Materials that are not available via major databases are often called grey literature. Grey literature may not be formally published or peer reviewed.

Knowledge about clinical practice guidelines and clinical trials are particularly important in medicine, but it also includes reports, statistics, conference papers, theses and dissertations, informal communication, websites, official documents, newsletters, and patents.

Have a look at the Grey Literature Resource Guide's Health Page.

You will find links to Clinical Practice Guidelines, Clinical Trials, Health Statistics, and Indigenous Health.