This plugin by Little Handy Tips uses the power of Google to search the contents on your wordpress site.
WordPress has a relatively good search functionality but tends to get sluggish and doesn’t match keywords that well. This is even more apparent when your site is quite large and you have many posts and/or pages.
Also Google Custom Search Engine is not limited to just your site. You can configure it through google to search multiple sites/domains. Or how about having a search Engine with searches all websites within your blog’s niche?
Combining Google’s search engine along the familiarity of their interface, this is a must have plugin for all websites.
The plugin is very flexible and you can configure the both the search box and the search results.
Google Custom Search widget’s search box can be displayed as either a widget or placed anywhere in the code (php and wordpress theme familiarity required to do this).
The search results can be displayed in one of three formats. *As a pop-up resizable dialog. *Within the widget, under the search box. *Displayed anywhere in the code (php and wordpress theme familiarity required to do this).
Plugin homepage: http://littlehandytips.com/plugins/google-custom-search/