Edyuk is a free, open source, fast and lightweight development environment which supports C++ and Qt 4 out of the box and can be extended through plugins. It works under all platforms supported by Qt 4 (Linux, Mac, Windows, BSD, ...).
Eryx is an experimental programming system with python-like main language syntax.
A Finite State Machine Editor, written on QT. It allows to draw Finite State Machine with easy GUI and store it in XML file. There are Finite State Machine Compilers to translate this description to source code (technique like QT's UIC uses).
Rapid applications development tool and libraries for FPC
The Lazarus IDE is a stable and feature rich visual programming environment for the FreePascal Compiler. It supports the creation of self-standing graphical and console applications and runs on Linux, FreeBSD, MacOSX and Windows.
DBG is a full-featured PHP Debugger and Profiler. Makes it easier to find problems or bugs in PHP scripts. DBG supports back-tracking, watching variables, viewing arguments passed to all nested function calls at any point of execution. Opensource.
xtrace - eXtended trace utility, similar to strace, ptrace, truss, but with extended functionality and unique features, such as dumping function calls (dynamically or statically linked), dumping call stack and more.