Getting a little, Search engine optimization-friendly corporate site behind a fundamental password protection plan, Let me give a fundamental search facility by utilizing among the off-the-shelf solutions. (I do not mind Google, or Yahoo getting the site's content, as lengthy because it does not leak towards the web).
Google does not appear to aid this, so Let me request the SO community for recommendations, and pros/cons of every (ideally free) solution? (Moving my very own may be the least prefered solution)
Wikipedia includes a nice listing of Enterprise Search Suppliers which links to details about all of them. It's a little hard to recommend certain ones not understanding what breadth of features you're searching for past text indexing.
If you're able to run PHP in your site, Wrensoft's Zoom Internet Search Engine is fairly good. It's free for sites under 50 pages, and cheap for bigger sites. I apply it my website at http://entrian.com/source-search/ if you wish to view it for action. (I am not associated with Wrensoft - only a happy user.)