Google Co-Op has released the first beta of Google Co-Op Custom Search Engines that allows you to customize the search results based on your website/blog or a favorite topic

With Google Custom Search, you can-

-Place a search box and search results on your website.
-Specify or prioritize the sites you want to include in searches.
-Customize the look and feel to match your website.
-Put your Google Adsense code to earn money from the search engine

Via Official Google Blog