http://www.keyworddiscovery.com/engines.html

Keyword Discovery currently collects search term data from just over 180 search engines world wide. Our database contains approximately 32 billion searches from the last 12 months.

   search engine optimization 3,638,572
   search engine optimization services 994,218
   search engine optimization company 524,587
   web search engine optimization 511,400
   dsl search engine optimization 118,512
   search engine optimization service 98,722
   search engine optimization specialist 55,744
   search engine optimization search engine placement 35,660
   search engine optimization google 31,108
   search engine optimization firm 28,555

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Compare this to Overture Tool

Searches done in April 2006

90814 search engine optimization
   15220 search engine optimization service
   13135 search engine optimization company
   10156 search engine optimization firm
   9360 search engine optimization specialist
   3067 affordable search engine optimization
   3017 search engine optimization certification
   2822 search engine optimization training
   2713 search engine optimization seo
   2599 company engine links optimization search