Grey Literature refers to the large volume of printed and electronic material that is not formally published but which is produced by governments, businesses, academics, non-profit groups, etc and often widely circulated.  Grey literature items are often known as "reports," "working papers," "white papers," etc.  

Since grey literature is not produced by conventional publishers, it is often poorly cataloged and difficult to find.  This guide provides some tools to help find these sorts of documents.  

For more information see Grey Literature in Library and Information Studies, a 2010 ebook on this topic.

Digital Commons @ Colgate
Colgate's recently created insitutional repository.

OpenDOAR
Directory of Open Access Repositories.

ROAR
Registrary of Open Access Repositories.

Disciplinary Repositories
Part of the Open Access Directory project at Simmons College.