We’ve seen much discussion from community members on integrating custom search capabilities into Magento. Google Custom Search is growing increasingly popular and allows you to harness the power of Google to create a customized search experience for your customers and add it to your Magento site. Using a custom search you can create a search engine that searches relevant parts of your site and helps customers find the products and/or information they are looking for quickly and easily helping to increase conversions and ensure that customers keep coming back for more.

via Magento – Blog – How to Embed Google Custom Search in Magento – eCommerce Software for Growth.