a versatile Integrated Development Environment (IDE) for C and C++ on GNU/Linux. It has been written for GTK/GNOME and features a number of advanced programming facilities. (same as http://anjuta.org/)
a free/open source, cross platform IDE. It is developed in C++ using wxWidgets. Using a plugin architecture, its capabilities and features are defined by the provided plugins.
open-source, cross platform IDE for the C/C++ programming languages (build and tested on Windows XP SP3, (K)Ubuntu 8.04, and Mac OSX 10.5.2). CodeLite is distributed under the terms of the GPL license.
integrates with Firefox to put a wealth of web development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page.
a free Ruby-based environment aiming to make programming easily available to beginners, especially children. Its driving force was an essay titled The Little Coder's Predicament written in 2003 by why the lucky stiff (AKA why)
the class libraries for Free Pascal that emulate Delphi. Free Pascal is a GPL'ed compiler that runs on Linux, Win32, OS/2, 68K and more. Free Pascal is designed to be able to understand and compile Delphi syntax, which is of course OOP.