Industry Associations offer a wealth of information on any specific industry. You can find an association for almost every industry. Industry associations, by the nature of their business model, stay close to companies and consumers who make up a particular industry. You can find industry data, consumer usage and behavior information, and (sometimes) association-specific surveys that offer in-depth insights about an industry.
Google: You can find association on Google by searching by the "industry name+ Association." For example, "Beverage+Association" brings up all different associations connected with the beverage industry.
There are a number of websites that offer important information useful in developing a business plan.