I use Zoom Search on one of the business sites I manage.
There's a free version but it's well worth buying. It's a breeze to implement and easy to modify the results page as well. You can make the results look just like any of the big SE's but you're in control. No ads, nothing to take visitors off your site.
You use software to spider your site and upload flat text files to your server. If you add/remove pages or content, just run it again, upload the files and you're good to go. The whole process takes mere minutes.
It'll even spider database driven sites just like any sitemap generator does. (Perfect for ecommerce sites).
Check it out
Zoom Search Engine - Add search to your website, intranet or CD/DVD
Wanna see it in action? Visit
Payroll Services Canada - Payroll Outsourcing solutions and give it a go.