With the Google Custom Search PHP SDK by Google, developers can interact the API to access search and customization features. It contains authentication with Api Key and authorization with OAuth 2.0. Examples demonstrate how to build the client object, build the service object, call an API, and handle the result.
MapQuest has launched another API on top of OpenStreetMap (OSM), the Wiki-like editable map of the world. The new search service provides geographic search results for any data added to OSM, such as streets or landmarks. Of note, the MapQuest API provides the service without any API Key requirements or rate limiting.
What could you do if you were spidering two billion web pages per day? Whatever your answer is to that hypothetical, you might as well do it now. The 80legs platform lets you write your own web crawler and sell your apps to users (our 80legs API profile). And if you can build it fast, there's an 80legs contest looking for your entry.