I came across a great tool today - Zoom. It allows you to add a fully customisable and unbranded search to your site. It can be javascript, CGI, ASP or PHP, so could also be used on a CD-ROM.
You can read more about it, and download the free version at
http://www.wrensoft.com/zoom/. The free version is limited to 50 pages, but this should be enough for many sites. I immediately bought the full version, and it is certainly worth it!
You can see that I've integrated it into my site using the Javascript version - take a look at
www.marketingyour.biz/search/search.html. (If you search for 'Teneric' you'll see the 'hidden' discount page that offers Teneric users my book at a discount (plug, plug).
Anyway, it's a great tool - look it up!