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I'll put in another vote for Inquisitor.

I think it searches Yahoo! by default, but you can make it search Google or Amazon or a few others, I think. I highly recommend it.
 
eeeemmmm, how so?

The drop-down box. I don't want it suggesting anything to me; I know exactly what I'm searching for. I just want to be able to switch rapidly between search channels and pull from a repository if I don't want to custom-add my own. Plus AcidSearch has a find-as-you-type option, too, for those who prefer it.
 
I prefer acidsearch as well, you can also highlight text and use the right click to search that text in the search channel you choose.
 
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