Google Web API is here
Google has published a beta of their Google Web API, which is a SOAP interface allowing your apps to search, retrieve pages from Google’s cache and request spelling suggestions (for which the enclosed XML samples show how to find out how Britney Spears name is spelled, of course).
The kit contains code samples in Java and .Net, samples of SOAP requests and responses and documentation. You have to register for a license key (for free) which enables you to do 1000 searches per day.
Update: Rael Dornfest has written a really nice walkthrough.