Trade, industry, and professional associations can be excellent sources for facts, statistics, reports, and can be a place to locate contacts to speak with about the industry.  Often (but not always) their data and reports are freely available on their websites.

Here are some resources that can help you to identify associations:

ASAE Gateway to Associations:
Searchable list of over 1,700 trade association homepages.

Encyclopedia of Associations
Descriptions of approximately 120,000 international and U.S. membership organizations in all fields.

Standard & Poor's NetAdvantage
Look at the section within each industry survey titled "Industry References" for a list of professional and trade associations for that particular industry.

IBISWorld
Look at the section within each industry report titled "Additional Resources"