From J.J. Hill library:
When someone hunkers down to do "market research" they can be embarking on about a thousand different journeys. They may focus on customers, competitors, industry data, or any number of other options - so having a guide to those options can help.
The Rutgers University Library offers one such guide, with this market research pathfinder. From commercial reports to government data and research centers, this collection (which focuses on consumer income, consumption, and demographics) highlights some of the best market research the Internet has to offer.
While a couple of the links within the guide don't go exactly where they intend to, the resource as a whole is an excellent intro to this multi-faceted research task.