In a keynote presentation, Eric Rudder, senior vice president of servers and tools, said Indigo is "a natural extension to the .Net Framework," which will enable developers to build more secure, reliable and interoperable applications on Windows that will be able to interoperate with other applications no matter what the underlying platform.More details at eWeek
Microsoft talks about its Indigo plans

Yesterday Microsoft unveiled its plans for building connected systems, by highlighting its next-gen Web services technology, code-named Indigo.