Bainternet

Not long a go google implemented an instant search functionallty that show resluts as you type even before you hit the search button. 
With This Plugin you can eaily add instant search functionalty to your site or blog.
Main features:
<ul>
<li>Very easy to install.</li>
<li>Easy configuration screen.</li>
<li>simple options to style the search results.</li>
<li>extendable by hooks and filters all around.</li>
<li>Use as shortcode.</li>
<li>Use as template tag for easy integration with your theme or plugin.</li>
</ul>
any Feedback is Welcome.
check out my <a href="http://en.bainternet.info/category/plugins" rel="nofollow ugc">other plugins</a>

Simple Instant Search

With This Plugin you can  eaily add instant search functionalty to your site or blog.

Anil Ankola

A WordPress Better Ajax Live SearchWP plugin created by Anil Ankola for your website live search plugin show instant search results as soon as you type in the keyword without reloading the page.
Features
<ul>
<li>Better Ajax Live SearchWP add menu in dashboard sidepanel</li>
<li>Better Ajax Live SearchWP choose background, title, text, button and separator color options in Better Ajax Live SearchWP menu settings admin</li>
<li>Shortcode System.</li>
<li>Use this shortcode [better_ajax_live_search] show live search.</li>
<li>WordPress Live Search Enabled.</li>
<li>Easy to Use.</li>
<li>You can use it in posts or pages.</li>
</ul>

Better Ajax Live SearchWP

Better Ajax Live SearchWP plugin is a live search plugin for WordPress without reloading the page.

Simple Instant Search vs Better Ajax Live SearchWP