Most established people probably already know about Mpire.com, but I think it's worth it to post it for newer folk who are confused about the best way to go about selling their products.
http://www.mpire.com/research/search.page
Don't worry - it's completely free. No catches. Apparently, no limit on the number of searches you can do (there used to be at one time, I believe) - at least, I've never hit any limits *shrug*
Strange that there's no limits, considering it uses Terapeak's API... but free is free, so who am I to argue?
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