Letting Amazon & eBay Work for You
eBay offers a Marketplace research service that costs $2 to $25 a month.
In addition to giving away this free conversion information, Amazon lets you see what customers think of the product via review, allows you to bid on keywords related to products via ClickRiver. If you sell your stuff on Amazon.com, you can buy a better together listing with a popular product.
If you are in the info-product market Clickbank’s Marketplace is a goldmine.
Once you find interesting products you can refine your keyword research using general keyword tools, then further refine that data by using a tool like KeyCompete to see what keywords competitors are bidding on.