Although it is sometimes hard to make work in all cases, I've recently moved a big project from MySQL to a Amazon's SimpleDB and S3 and it has turned out awesome. You have to design the system from the ground up to deal with the 'eventual consistency' problem, but that problem is fairly tractable and easy to wrap your head around. And the reward is 'infinite' scalability and no single points of failure. Good stuff. SQL is still great for the simple projects where you don't need to worry about uptime or scalability, but for everything else I'm sold on AWS (or BigTable)