I recently heard about the Windows Live Platform (WLP).  This describes cloud-based services from Microsoft that are available to web developers.  The developer page is at dev.live.com.  Many of the services are currently in beta.  The most exciting services center around Messenger (share this page with a friend), Search, Virtual Earth (maps), Silverlight Streaming (free video hosting with generous terms), and Application-Based Storage (cloud-based state management). 

On a geeky-cool note, this is also the dev center for Windows Live Writer and Web Gadgets. 

There is a Windows Live toolkit for Visual Studio 2008.

Have fun writing code with the cloud.  Please share your stories about using WLP.