Windows 7 supports a new feature called Federated Search. It’s based on OpenSearch and RSS2 and enables searching of remote repositories from the Windows desktop. Developers have created some really interesting search plugins that allows users to search Flickr, Twitter, Deviantart, Google News, Yahoo and YouTube right from the desktop search in Windows 7.
To get going, all you have to do is download and open the OSDX file and Windows will automatically add the site to your saved searches folder. Then you need to goto Library –> Searches. And select the search you want to use.
Here is a list of all Search Connectors for Windows 7.
NOTE: These connectors work with Windows 7 Build 6801 (PDC 08 Build) and above. (Includes Beta - Build 7000). IT DOES NOT WORK WITH WINDOWS VISTA.