Does federated search option works to crawl external websites which are of non search engines. As i heard it is used for external search engines to get data in search results but can it be used for external sites as well.Please suggest me some ways where we can crawl external non SharePoint websites to crawl in SharePoint 2010 search.
Federated search will not do that. You'd need to configure a content source pointed at the external site, crawl that, then search against a scope created to look at that content source.
Federated search points directly to other external search engines.