Here’s quite a good (short) paper on the past, present and future trends in research on search engines. It is entitled, helpfully enough, as “Shifts in Search Engine Development: A Review of Past, Present and Future Trends in Research on Search Engines“.
This paper was written in 2004, and provides an easy-to-follow overview of search engine technology. Of interest to search marketers is the development, and methodology, of document sorting. Nothing too deep here, but as I say, a good overview on the topic.