There was some ancient DOS "e-book" software I had as a young kid that had something like this (e.g. Find "Jacob" within 32 words or 6 verses of "Esau"); finally I know how to do the same thing with the web.
Another thing to add the the Google-Fu toolbox. I wish I had this a bunch of times, since sometimes blogs will appear in search results that mention two topics I'm interested in, but not in the same article.