Just announced. Although Google search has always been available for websites, this time it’s with a difference. Now more like the search provided by atomz, the results can be tailored more to your liking based on your theme/content. You can even add multiple websites to be searched, which opens up a whole load of possibilities.
Say for example I start a search engine on error messages in wordpress. 🙂 So I add a bunch of websites to be searched, and others using Google Co-op can add other helpful sources they come across. In time, this search becomes the definitive search engine for wordpress troubleshooting.
Setting up is simple enough. Get started here with Google Co-op.