Watch: An Introductory Tutorial
Associations: Trade, industry, and professional associations can be a great source of information. They may have data available on their website, or contacting them might result in good leads. A search in Google is the easiest way to identify associations.
Proxy Research: It's hard to find secondary research on innovative or niche markets. Try to think of a proxy--an analogous product, use-case scenario, or target.
Market or Target? Look for reports on your product category, but also reports on your target. A 200-page report on the American Mother may not mention your product category, but if that's who you're targeting, it will likely provide valuable insight into that target.
Industry vs. Market Research: Start with industry research, then move on to marketing. Industry research focuses broadly on industry size, outlook, and structure. Market research is narrower and adds emphasis on branding, trends, and consumer behavior. Market research firms specialize in certain industries and are more likely to conduct primary research. A high-quality industry report might be 20-30 pages and cost $1,000, while a good market research report can be 200 pages and, depending on the industry, from $4,000 to $15,000.