Orange 3D, a game engine distributed under the zlib/libpng license, is an all in one solution, with IDE, level editor, 2d painter, 3d modeler, and possibly audio editing software all in one clean package, for free!
An environment (library + IDE) that emulates Delphi but uses python as the programming language and wxPython as the graphical API. Starting with the library, we have a set of modules/classes that emulates the units/classes of the famous VCL.
RGnome is a gtk based frontend for GNU R, which is a widely used language for statistical computing. It features a fully working R console and an editor with syntax highlighting.
This is project is a refactoring assistant kit. It intends to provide tools and script to help refactor C++ code, replacing our usual search'n'replace by providing some rough code analysis and IDE specific plug-ins for integration.
Don't write that regex, grow it! Regex Garden aims to create a simple, easy-to-use graphical interface for building, testing, and debugging regular expressions. Simply stated, it's an IDE for your regular expressions.