Grey literature is the unpublished, non-commercial, hard-to-find information that organizations such as professional associations, research institutes, think tanks, and government departments produce.
It can be invaluable to your research: it is part of the overall evidence base and functions as an alternative source that may be used to overcome possible bias presented by published information.
While the bulk of the information here is related to the health sciences, there are general resources (databases for disserations and Scopus and Web of Science, which provide broad coverage of subjects), plus links to more technical (i.e., engineering) and hard science resources on the Other Resources page.
Searching for grey literature can be time consuming because it is not usually included in bibliographic databases. Therefore, knowing how to search correctly for grey literature can help you use your time as effectively as possible.
On the Strategies for Finding Grey Literature page, you'll find a quick introduction to ways of thinking about searching for grey literature.
Remember, don't hesitate to ask your informationists if you need help.