Grey literature is information produced outside of traditional publishing and distribution channels. 
Examples
Reports, (research or annual reports)
working papers,
newsletters,
government documents,
speeches,
white papers,
urban plans, and so on.
Google is the easiest way to find Grey Literature like company reports.
More Information:
Organizations such as businesses and charities along with Governments, regularly publish reports, white papers, statistics and other documents. Their intended audience could be the general public or stakeholders. These reports can be a key source for emerging research and alternative perspectives. However, these sources are not reviewed by peers and some are intended to promote the agenda /ideas of the organization.
Reports & publications from governmental and nongovernmental organizations
Technical reports and standards
White papers
Annual reports
Conference proceedings and abstracts
Newsletters
Thesis and dissertations
Can be well researched,
Current coverage of emerging issues
Local and Canadian content
Data and statistics
Different viewpoints from standard academic articles
The best place to start is with Google. Use Google's site search to limit to a government or institution's site or top-level domain;
This technique paired with keywords in Google is a quick way to locate grey literature, you can use it with any URL. Sample search: site:gov.on.ca rental housing
Find Canadian Government Publications on the Web (from Carleton University )
Open Grey searches grey literature published in Europe
Catalog of U.S Government Publications is a finding tool for U.S government publications