Amazon Web Services

"Amazon is starting to rent out just about everything it uses to run its own business, from rack space in its 10 million square feet of warehouses worldwide to spare computing capacity on its thousands of servers, data storage on its disk drives, and even some of the millions of lines of software code it has written to coordinate all that." - Business Week: Jeff Bezos' Risky Bet

Actually Quite fantastic services to use for small projects and companies that need reliable solutions that can scale to the infinite! I only have used Amazon Simple Storage Service (s3) so far. And tested one of the Alexa Web Services so far... works well!