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.

jameelbokhari

Awesome Instant Search integrate Instant Search to ANY wordpress website using CSS seletors. If you are familiar with CSS already, you should have no problem setting this up. The less experienced can use <a href="http://www.jameelbokhari.com/awesome-instant-search/" rel="nofollow ugc">my full tutorial</a> to set up in 15-20 minutes.
After installing the plugin, go to Settings->Awesome Instant Search in your admin panel. On the first tab, General Settings, you can activate the plugin, but you should probably set it up first.
If you are working with the TwentyThirteen theme, the plugin should work out of the box. 
TwentyTwelve and TwentyTen can be applied instantly as well. Go to the plugin settings page described above, and under the General Settings use the dropdown next to Theme Quick Settings to select between twentythirteen, twentytwelve and twentyeleven. Again, if you are not using these themes you have to set the plugin up to fit your particular theme. Unfortunately there’s not a way (that I know of) that will get this plugin working out of the box!
For the quick tutorial, see below. For those of you unfamiliar with simple HTML and CSS concepts, <a href="http://www.jameelbokhari.com/awesome-instant-search/" rel="nofollow ugc">see my full tutorial</a>.
<h4>The Essentials</h4>
Essentially, you need to configure three settings.
<ul>
<li>Search Field Selector</li>
<li>Page Content Selector</li>
<li>Search result selector</li>
</ul>
If you know your <code>HTML</code> pretty well, here’s what to do: Assign Search Field Selector to the class or ID of your search field(s) in your website. The default <code>input[name="s"]</code> should work for any website.
Assign Page Content Selector to the ID of the element you want your search results to appear in. Remember to use a period (.) or hash sign (#) just like you would with a <code>CSS</code> selector. So for example <code>#content</code>. Just like with CSS you can be more specific when you need to, e.g., <code>#main #content .container</code> and so on. Keep in mind, this content will be hidden on the current page where the search is performed.
Next, in the same fashion, assign a selector for the search results. In about 99% of websites, this is going to be the same as the content selector with .hentry added in there. For example, if you assigned <code>#content</code> as your Page Content Selector, you would use <code>#content .hentry</code> as your Search Result Selector.
These are the three most important settings. After you get these, go ahead and test it out or play with the other settings.
<h4>Other Settings</h4>
Search URL is where the search results appear. This is your wordpress website’s domain with the letters <code>?=s</code> appended to it — e.g., http://www.example.com?=s 
This shouldn’t need to be changed but is there just in case you ever need to change it.
Hide These Elements If you want additional elements to be hidden when performing a search, use this option. These elements will be revealed again when the search is cleared. This value accepts comma separated <code>CSS</code> selectors, use it to hide comments, page navigation and other extraneous elements when searching.
Before Instant Results is <code>HTML</code> to appear before the Instant Search results. Use the tag %%SEARCH_TERM%% to print the search term, e.g., <code><h3>Search results for: "%%SEARCH_TERM%%"</h3></code> might show up as <code><h3>Search results for: "Contact Info"</h3></code> on your page.
Theme Quick Settings Quickly access default settings for twentyten, twentytwelve, and twentythirteen.
<h4>Translation</h4>
<ul>
<li>Español <a href="http://www.webhostinghub.com/" rel="nofollow ugc">Maria Romos with Web Hosting Hub</a>.</li>
</ul>

Awesome Instant Search

Awesome Instant Search integrate Instant Search to ANY wordpress website.

Simple Instant Search vs Awesome Instant Search