At the PDC 2008 keynote a few minutes ago, Ray Ozzie, Chief Software Architect at Microsoft, anounced the CTP of a new platform that takes the Windows brand: Windows Azure. Here are some links:
Basically Windows Azure is a new operating system running in the "cloud". As part of Microsoft’s Cloud Services play, Windows Azure gives developers a scalable platform for building and deploying applications. One of the speakers who just spoke demonstrated a social network application built on Azure and Silverlight.