Google just launched a customized search service called Google Co-op to bring tailored search to Web sites and blogs. Co-op allows a user to use the Google search platform to create a search engine focused on any content they want with just a few specific websites included. Searches will return results only from the sites the user requested.
Users have a number of options to customize the search engine: choosing which pages they want to include in their index, how the content should be prioritized, whether others can contribute to the index, and what the search results page will look like.
This can be particularly useful for small websites and blogs who wish to monetize their search as the service can be integrated with Google Adsense. The Google Co-op search would be a better choice for bloggers than their default built-in search feature as they can create a search engine with just one site, namely the link to their own blog/website. It allows a kind of social search by allowing other people to add links to the search results and also allows sharing of revenue with those sites who embed your custom search engine into their site.