Ranking these Engines is a little difficult but, here is an attempt:
Google NineMSN (more beginners) Yahoo ANZ (little bit difficult to tell where this traffic is coming from) Sensis Webwombat Ansearch
I think the first two would account for 70+% of the market. It depends on how your measure your search engines: Number of searches made Number of people conducting search Amount spent based on searches Margin generated based on sales generated from searches
-Google by a clear, clear margin - larger than the next 2 SEs combined in just about any metric. -NineMSN -Y! ANZ
After this is a legion of SEs who each have less than 4% active reach - Optus, Sensis, Ansearch, Webwombat, Alta Vista, Ask Jeeves etc. Volume of web page views is pretty similar. That data is pretty sound although I don't have it in front of me atm.