On the O'Reilly OnLamp.com website today, there's a new article that compares searching methods on a site - a "search engine showdown".
It's a universal frustration. You just know that the piece of information you're looking for is somewhere on a site. You click one link, then another, and another. You go back to the home page and try a different branch of the site. After dozens of clicks, you still can't find the information you need. Then it's back to Google and on to another site. At last you find one with an internal search engine. You enter your search term, and voilá!--the information you need pops up in less than a second.
They compare these two types - hosted versus local - and show how to get started on integrating one, the local option, into your site. They start with a few things consider before getting into the choices - the physical issues involved, the page information itself, and how the engine will index.
The rest of the article is devoted to the different options they'd recommend along with ratings, what technology they use, if they're PHP5 compatible, difficulty of installation, and many more criteria. Their list of leading local search engines for your site are: