Here’s Compete’s relative ranking of the top search engines for December 2006:
And here’s comScore’s December 2006 US market share data (6.7 billion total searches):
The two sites disagree on Yahoo! and AOL directionally. For Yahoo! comScore shows a gain; Compete shows a loss of share. Regarding AOL, Compete shows a bit of a recovery while comScore shows further erosion.
To throw in a bit of local search perspective: the local products of the majors are capturing about 1% of the traffic of general search. comScore says local search is 13% of all search but it’s a much bigger number when you consider (per WebVisible-Nielsen research) that as much as 51% of local search queries don’t carry a geographic modifier.
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Related: Danny Sullivan’s extensive discussion of Microsoft’s challenge to build share in search. And a long, traffic trend analysis.
Screenwerk 
January 16, 2007 at 4:23 pm
With regard to all the many avenues to increase local search to a site, the dominant process by users remains long tail search terms within the SE’s. As a practitioner of a local business/service, to date the 2nd most powerful source for leads is local usage of craigslist as appropriate. As you mentioned, many terms for a service, and my service in particular begin with a non-geographical search- that is direct and anything but long tail. Hence PPC becomes critical.
In that regard, G dominates the long tail search terms as it does total SE traffic.
Dave