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.
wspacegen is an interactive IDE for programing with whitespace (http://compsoc.dur.ac.uk/whitespace/). So it's possible to create .ws code relative easily and debug it as well. But attention, you'll addicted to it (-:
Mipscope is a cross-platform IDE for students learning assembly on the MIPS architecture. The focus is on a convenient debugging environment, including a visual, reversible debugger.