Here. "The KDE Project has emerged as possibly the first real-world adopter of Project Mono for application development. Mono is an open source alternative to .NET for Unix and Linux desktops, initiated in July 2001 by Ximian Inc."
The reason that this is interesting for Windows developers is that with both of the major Linux desktops, i.e. Gnome and KDE, supporting .NET, it's possible that a simple .NET application or component could actually work across Windows, Gnome and KDE. Now .NET becomes the OS. Shades of Java, which failed in this space I know, but still interesting...
