The Google Ad Grants program supports nonprofit organizations in the U.S. and overseas. It is a unique in-kind advertising program that harnesses the power of the company's flagship advertising product, Google AdWords. Through the program, selected organizations receive $10,000 per month in in-kind AdWords advertising to promote their missions and initiatives on Google.com. Online applications may be submitted at any time. Visit the Google website for program details.
More info here: https://www.google.com/grants/