An MS dev guy wrote BlindSearch, a simple web-s’ware page to compare the Google, Bing, and Yahoo search engines:
Type in a search query above, hit search then vote for the column which you believe best matches your query. The columns are randomised with every query. The goal of this site is simple, we want to see what happens when you remove the branding from search engines. How differently will you perceive the results?
Your search results appear in three unlabeled columns. You then vote for the one with the best results and the search engine for each column is revealed.
They had to turn off the totals for now (“Some douche is gaming the system, I’ve removed the ability to see the results until I sort this out.”), but at last tally it was: Google: 44%, Bing: 33%, Yahoo: 23%.