In October 2008, Americans conducted 12.6 billion core searches, up 7 percent versus September, as Google Sites maintained its top position with more than 63 percent of all core searches conducted.

Google Sites led the U.S. core search market in October with 63.1 percent of the searches conducted, up 0.2 percentage points from September, followed by Yahoo! Sites (20.5 percent), Microsoft Sites (8.5 percent), Ask Network (4.2 percent), and AOL LLC (3.7 percent).

http://www.comscore.com/press/release.asp?press=2601