GNOME Builder!

Notepad++ is a free source code editor and Notepad replacement that supports several languages.

Sublime Text is a sophisticated text editor for code, html and prose - any kind of text file. You'll love the slick user interface and extraordinary features.

Microsoft Visual Studio is an integrated development environment (IDE) from Microsoft. It is used to develop computer programs for Microsoft Windows, as well as web sites, web applications and web services. Visual Studio uses Microsoft software development platforms such as Windows API, Windows Forms, Windows Presentation Foundation, Windows Store and Microsoft Silverlight. It can produce both native code and managed code.

Brackets is an open-source editor for web design and development built on top of web technologies such as HTML, CSS and JavaScript. The project was created and is maintained by Adobe, and is released under an MIT License.

A free, open-source Integrated Development Environment for software developers. You get all the tools you need to create professional desktop, enterprise, web, and mobile applications with the Java language, C/C++, and even dynamic languages such as PHP, JavaScript, Groovy, and Ruby. NetBeans IDE is easy to install and use straight out of the box and runs on many platforms including Windows, Linux, Mac OS X and Solaris.The download section conveniently offers prepackaged bundles/installers for each supported programming language containing only required plugins. »

GNU nano is a small and friendly text editor. Besides basic text editing, nano offers many extra features like an interactive search and replace, go to line and column number, auto-indentation, feature toggles, internationalization support, and filename tab completion.

GNU Emacs is an extensible, customizable text editor—and more. At its core is an interpreter for Emacs Lisp, a dialect of the Lisp programming language with extensions to support text editing. The features of GNU Emacs include:

Code::Blocks is a free C++ IDE built to meet the most demanding needs of its users. It is designed to be very extensible and fully configurable.

Komodo Edit is a fast, smart, free and open-source code editor. Switching your trusty code editor is hard, but give Komodo Edit (or its big brother Komodo IDE) a try: it'll be worth your while.