Is there any one book or resource on search engine development & theory?
michael_dorfman: There are some ACM/IEEE journals that have relevant papers, but you have to ask yourself: is reinventing the wheel what you really want to be doing?  Given that there are lots of available COTS solutions, shouldn't you be focusing on things that are unique to your app?(Needless to say, if the search engine needs are unique to your app, and a COTS solution isn't viable, you might want to bring in someone with relevant expertise.)