Glad you asked.
There are really only 4 search engines that you need to concern yourself with, they are:
Many people might throw in favorites like:
I don’t consider About.com an actual search engine, but they do have lots of hand picked links and information there. As for the Top Search Engines List I mentioned above, only 2 of those 4 search engines even use keywords anymore.
Yahoo and Ask.com are the 2 search engines using keywords as relevant search criteria.
Update: Jan 22, 2011 –
There are now only 3 search engines that you need to concern yourself with, they are: