depending on how big your site is, you can use Google API and put there search engine right into your homepage for free! You would be limited to 1,000 queries via this method,

or you can link to google directly via a form box
[html]<form method="get" action="http://www.google.com/search">
<input type="text" name="q" value="">
<input type="hidden" name="as_sitesearch" value="www.daniweb.com">
<input type="submit" value="Google Search">
</form>[/html]

just make sure to replace www.daniweb.com with your domain name, but there are drawbacks, once the user clicks search, they have left your webpage and then can modify the search and remove your site name, so now they are searching the web and not your site.

if your site isn't too big I would definatly recommend working with the google api to search your site, send me a private message if you need help setting up a search with the google api and I will be glad to help.