Easy to use Ghostscript IDE.
Allows you to easily edit and view PostScript (multi-page PostScript) files, convert your files between different formats (PDF, PostScript, TIFF, PNG, JPEG, other...), view PDF files.
Please go to http://ghostscriptnet.codeplex.com/ for development files.
xacc.ide is a opensource IDE aimed at mainly .NET development. It has a code editor written in 100% C# code, which is faster than most commercial offerings.
Zero Button Testing: a Pythonesque programming language with integrated unit testing and an editor that takes advantage thereof, with correctness and coverage highlighting. Written in C# on Windows' .NET platform.