After putting in my request to Google I found a number of lists.
Here are a few, there are quite a number of others.
http://www.thesearchenginelist.com/
http://en.wikipedia.org/wiki/List_of_search_engines
http://www.searchenginecolossus.com/ (for international search engines, arranged by country)
These lists include an amazing number of search engines on a variety of topics, from the law, to jobs, to blogs, to games for example and also have metasearch engines, such as Dogpile, and Zuula which will search up to sixteen other engines for you.
One that wasn't included was one I used to use a couple of years ago to winkle out obscure pieces on Conductive Education. This was called Bananaslug and I was reminded about it this morning by Andrew.
It can be found at http://www.bananaslug.com/ and is called a long tail search engine as it takes random words you select and uses them to find hits on a particular subject. For example, you could choose Conductive Education as your subject and add random words from one of a number of categories listed on the site, e.g. emotions or first names for instance, to make a search.
I will have to investigate as many of these as I can and see what I can find. If you do the same, please do let me know of any items of particular interest that you consider should be included in the virtual Catalogue on http://www.e-conduction.org/
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