Well, the most easily to set up search engine that comes to my mind right now would probably be Google’s Custom Search Engine
. Of course that ease comes with a price, not in money but in the searches probably being tracked and analyzed by Google for further action (e. g. serving personalized ads or handing the search and browsing behavior over to the NSA).
If you are familiar with Java you could search for a JSP solution, perhaps there are premade scripts already (I can’t give you any hint there)? That requires special set-up of the servers, though, because JSP isn’t running natively on either Apache or IIS (but can be added as extension).