It is still in development stage though, only version 0.1, no ads are in the search results for now, but in the upcoming version 1.0, Google says it will have ads, maybe a good news for AdWords Publishers. The search result covers 4 categories or more like 4 different search types. The categories are Local,Videos,Web and Blog; all of them are self explainatory. I find this quite a useful feature, as you might want your search to be more broader,covering not only websites. But i would suggest adding an Image Search category as well, to complete the whole package. The final characteristic of the API is that the search results may also be expandable up to 8 items per category, and retracted to show only one item. I have made a test page for this, so you can play with around ;) : Google Ajax Search API