Indigo and Avalon are the codenames for two strategic developer technologies that Microsoft plans to ship in 2006 as part of the Windows "Longhorn" operating system. In addition, Microsoft is making these technologies available on Windows XP and Windows Server 2003. The Indigo and Avalon Community Technology Preview (CTP) enables developers to experiment with early builds of these technologies, get acquainted with the development experience, and provide Microsoft with feedback. This CTP release recently became available to MSDN subscribers and is now being released to the general public in response to numerous requests. More details about these technologies are below.

Avalon and Indigo Community Technology Preview - March 2005

Thanks to Neowin.net