As mentioned prior, one of the many forms of grey literature includes conference materials or presentations. These resources can be found in many places including databases as well as online via the conference host's website. See below for more information on these pathways.
Several of the aforementioned databases specifically offer grey literature in the form of conference materials.
For some databases, researchers can narrow search results by material type. Depending on the database, the language used may vary. Conference materials could be listed as:
Some conference papers or proceedings may be published or made publicly available freely on the Internet from their own website. Authors should look into past conference proceedings from relevant affiliate organizations in order to become aware of any unpublished presentations or papers written on the subject. (For example, the American Association for Cancer Research publishes proceedings from past meetings on their website - shown below).
However, not every organization may do this or have clear designation of past conferences on their websites. It can also be helpful to use a search engine like Google to search for past conference programs if they're not easy to find on an organizational website.
The two pathways to finding conference programs listed above only begin to cover the numerous online rabbit holes where conference information could live. Iowa State University has an excellent resource available on how to find conference proceedings available here. The tab of "How are They Made Available?" outlines even more ways that conference materials can be categorized or buried.
As always, in addition to this resource, you can contact a librarian for any questions or help in finding conference papers.