Hot from the PDC: Windows Azure
Windows Azure is the Microsoft awnser to the Google App Engine and Amazon EC2. Basically it is a platform in the cloud for developing web applications. It isn't just about hosting ASP.NET applications but also about services like SQL Server and SharePoint Server. You basically use Visual Studio and the languages like C# or VB ou already know. Development is local using a development server that mimincs the Azure network, just like Cassini mimicts IIS during development. And ofcouse Azul also contains workflow services
Windows Azure is the development, hosting, and management environment of the Azure Services Platform, which enables you to run applications at Internet scale while leveraging the skills and tools you use today.
Windows Azure Tools for Microsoft Visual Studio extend Visual Studio to enable the creation, building, debugging, running, and packaging of scalable services on Windows Azure.
see http://blogs.msdn.com/cloud/ or http://www.azure.com for more details.