MonoDevelop enables developers to quickly write desktop and web applications on Linux, Windows and Mac OS X. It also makes it easy for developers to port .NET applications created with Visual Studio to Linux and Mac OS X maintaining a single code base for all platforms.
a free source code editor which supports several programming languages running under the MS Windows environment. based on Scintilla edit component (a very powerful editor component)
Intype is a powerful and intuitive code editor for Windows with lightning fast response. It is easily extensible and customizable, thanks to support for scripting and native plug-ins. It makes development in any programming or scripting language quick and
Gobby is a free collaborative editor based on libobby, a library which provides synced document buffers. It supports multiple documents in one session and a multi-user chat. It runs on Microsoft Windows, Mac OS X, Linux and other Unix-like platforms.