If you are a simple soul, and only infrequently need more from your search engine than a blunt keyword search (Oregon legal research, for example), iLibrarian links to this post: 100+ Alternative Search Engines You Should Know.
I especially liked the list of E-Book & PDF Search Engines. These are good complements to a Google’s filetype search. And, sometimes you just need more than one search engine. The Google search is a bit more useful in that the size of the publication can be seen more quickly, and you can choose to view the document in HMTL, as an alternative to the PDF. But these others search engines have their own strengths and you don’t have to be a Super Searcher to make good use of them.