Anyone out there with a great idea for building a startup around Amazon Web Services can enter a $100,000 challenge that Amazon is sponsoring. Amazon’s collection of Web infrastructure services include hosted storage (S3), compute cycles (EC2), computer-to-computer messaging (SQS), payments (FPS), and an on-demand workforce (Mechanical Turk). AWS has already attracted more than 265,000 developers. And some of the services are growing at a nice clip. For instance, S3 has gone from storing 800 million files in July 2006 to 5 billion files in April 2007 to 10 billion now in October. So usage of S3 alone has doubled since last April. Companies like Zillow already base their Websites on Amazon’s back-end infrastructure. Amazon wants to get a lot more.

The $100,000 will be split in half between $50,000 cash and a $50,000 credit for Amazon’s infrastructure services. The winner will also get an investment offer from Amazon. The deadline for applying for the prize is October 28.