Accumulating most common queries (for possible keyword analyses)

I know that some search engines allow you to ask what the most common queries (that included a particular keyword) were.

I can only find
http://inventory.overture.com/d/searchinventory/suggestion/

but I assume it must be possible for other searh engines, since Wordtracker claims
"We compile a database of terms that people search for. You enter some keywords, and we tell you how often people search for them, and also tell you how many competing sites use those keywords"

Can anyone direct me to the URL's for the major search engines where I can find these common queries, for a particular keyword.

Thanks