Amazon announced the use of Microsoft Windows Server on Amazon EC2 later this fall, that will let you host highly scalable ASP.NET sites, high performance computing (HPC) clusters, media transcoders, SQL Server, and more. You can run Visual Studio (or another development environment) on your desktop and run the finished code in the Amazon cloud.
The 32 and 64 bit versions of Windows Server will be available and will be able to use all existing EC2 features such as Elastic IP Addresses, Availability Zones, and the Elastic Block Store. You'll be able to call any of the other Amazon Web Services from your application. You will, for example, be able to use the Amazon Simple Queue Service to glue cross-platform applications together.
Existing EC2 tools will be able to launch Windows-powered EC2 instances. Once launched, you can use the Windows Remote Desktop or the rdesktop tool to access your instances.