I've updated the long-standing comScore Media Metrix Search Engine Ratings and Nielsen NetRatings Search Engine Ratings pages I maintain with figures that show search engine popularity for December 2004, the latest available.
The comScore figures show Google still with the largest slice of the search pie though Yahoo is just barely behind. But Google's share is larger when you factor in the searches at AOL that it powers. Also please note that technically, MSN wasn't providing its own results that month, as shown on the provider pie. But it's better to show it that way and avoid confusion with some who will view it, given that MSN is now a provider.
The NetRatings figures give you a look at more than just the very top search engines, instead stretching to the top 15. But some of those will probably have some of you scratching your head. Information.com is more popular than Netscape Search? But note the average search time figures also shown. They indicate places people might go and stay, as opposed to wind up on somehow and depart quickly.
The NetRatings figures also don't show the entire share of search but as explain on that page simply reflect "audience reach," whether someone simply did even one search at the search engine in a given month.