vladff

Using TB Search in Menu you can easily add a search item in your menu that will show a modern search form when clicked. All you need to do is activate the plugin and choose the menu location where you want your search item to be shown. 
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TB Search in Menu

This plugin adds a search item in the nav menu of your choice

Jupitercow

This plugin was completely rebuilt from the ground up on August 21, 2012. It now works using the placeholder attribute.
This plugin adds an options page to change the default text that shows in a search field. If your theme’s search input already uses a placeholder, this will change it. If your theme does not use a placeholder, this will add one with javascript. It also adds IE support for the placeholder attribute. Default text will start showing up in IE once you activate this plugin.
Enhanced Search Box Benefits
<ul>
<li>Allows control over the default search box text from the WordPress Admin</li>
<li>Uses modern HTML5 placeholder attribute</li>
<li>ADDS PLACEHOLDER SUPPORT FOR IE!</li>
</ul>

Enhanced Search Box

Add extra functionality to default search box using jQuery.

TB Search in Menu vs Enhanced Search Box