Amazon Web Services provides businesses a variety of business services on a per-use basis without requiring users to pay up-front expenses or make long-term commitments. Users can choose whichever development platform or programming model that most suits their needs. Amazon Web Services announced in early December 2008 that it would begin offering unlimited public beta of its service Amazon SimpleDB.Amazon Web Services: What is AWS? MarketWatch: Amazon Web Services Announces... (December 1, 2008)

• Free tier of usage
• 25 machine hours per month
• 1 GB of data transfer in and out
• 1 GB of storageMarketWatch: Amazon Web Services Announces... (December 1, 2008)

• No contracts or commitments
• Pay as you go
• Transparent pricing
• Better economics
• Better use of your time
• Better environmental impact

• Scalable
• Able to handle spikes in usage
• Reliable and redundant
• Experienced
• Secure

• Platform agnostic
• Ready on day one
• Application services

• Amazon Elastic Compute Cloud (Amazon EC2)
• Amazon Simple Storage Service (Amazon S3)
• Amazon CloudFront
• Amazon Simple DB
• Amazon Simple Queue Service (Amazon SQS)

Windows Azure Platform
http://www.microsoft.com/azure/

Google app Engine
http://code.google.com/intl/en/appengine/

Caroline Project
https://www.projectcaroline.net

Elastra Enterprise Cloud Server
http://www.elastra.com/products/elastra-enterprise-cloud-server