List of programing editors that are Open Source

Notepad++ is a nice source code editor
Code blocks is a cross platform IDE
Cygwin is a compiler that build Linux source code from scratch.
Eclipse is C++ and java IDE
SharpDevelop is a free IDE for C#, VB.NET and Boo projects on Microsoft’s .NET platform. It is open-source, and you can download both sourcecode and executables from the site.

And don’t forget Geany!