3 is MSN (Live) Search. The total market percentages vary depending on whether you're talking about total searches, total unique users, PPC advertising revenue etc.
Yes, it also depends based on country too. Yahoo does better in the most important market (U.S.) compared to how they do in other makerts.
Keep an eye on everyclick.com, it is sending me thousands of visitors per day and is powered by Ask.com.
As of July 2006. Google - 49.2% Yahoo - 23.8% MSN - 9.6% http://searchenginewatch.com/showPage.html?page=2156451