@neelsheyal, Google allows custom search but for a small fee, otherwise you are very limited in the way you display results.
For free you can use the Google Custom Search:
For a payment you can use Google Site Search:
A better alternative, and the one I use is the Bing Search API.
Specifically the Bing 2.0 API
The Bing Api Is Free! Its ad free, and amazingly quick. There are already some libraries for searching through JSON, C# etc. But since the results are XML you can process them however you want. I recently wrapped up a project that used Bing Search using Classic ASP, and we used some Jquery code to make our own version of Instant Search Results which came out very nice.
With Both Google and Bing you have to do a little bit of programming. I think you are better off going with the one that is free.
2nd note. Google indexes far more pages than bing does. Using the bing search API makes sure we focus on making sure that all search engines index our pages not just google. It almost forces you to focus on better SEO which is a good thing.
Let me know if you need some code samples.