Microsoft has just released their version of cloud services like Amazon's S3, SimpleDB, Google's App Engine, etc... called Azure Services Platform. It is still in beta. As per Microsoft Azure Services are available without charge during Community Technology Preview (CTP).
To learn more go to Azure's site http://www.microsoft.com/azure/default.mspx
To play with this new services download the corresponding SDK from http://www.microsoft.com/azure/sdk.mspx
They also have a training kit available here http://www.microsoft.com/azure/trainingkit.mspx