I believe that the more competition there is the better it will be for us the consumers and for capitalism's health (that's what capitalism is). This is why I want to give exposure to relatively unknown sites along with the more well known ones. I don't want any single search engine on this list to cease operation. I appreciate and use them all.
I want to give a special mention to yasni.com It's primarily a people search engine but in the results it displays a link to it's web search. The results are "unconventional" compared to other engines. you'll find obscure yet good websites you've never heard of.
http://www.yasni.com/ (yes it has "annoying" pop ups but for a knowledge junkie like me thats just part of the fun)