GreenMaven offers a ‘green-focused’ search engine that takes advantage of Google’s Custom Search feature that makes it easy for any blog or site to add their own customized search engine. Theirs is a great implementation of this very cool technology.
In my other life as an SEO/SEM guy, I’m very interested in the potential of targeted search that combines Google results with expert editing by actual humans. For those interested in environmental issues, the GreenMaven people have assembled a very useful resource. If you have a greenish blog or site you might want to join them.

BTW, if you’re interested in making a few bucks with your site, Google will share ad revenues from clicks that take place in your custom search engine’s results.