Arabeske is a special kind of vector drawing software. It has a limited set of shapes but is extremely specialised towards complex symmetric interlaced drawings, like those traditionally found in Arabic architecture. It is not a texture editor, but rather a pattern generator. It exports in EPS, PNG, and POV-Ray formats.
DAP is a comprehensive audio sample editing and processing suite. It currently supports AIFF and AIFF-C audio files, 8 or 16 bit resolution, and 1, 2 or 4 channels of audio data. The package offers comprehensive editing, playback, and recording facilities including full time stretch resampling, manual data editing, and a reasonably complete DSP processing suite.
Dia is a program for creating diagrams of all kinds. The current version can do UML class diagrams, Entity-Relationship modeling, network diagrams, and much more. The engine is very flexible and dynamically loads diagram-types from disk. It stores diagrams in an XML format, but can read and write a number of different formats.
DiaCanvas is a generalized version of the drawing canvas used by DIA. It extends some features used by DIA and adds new ones, while preserving as many of the original features as possible. This project is no longer actively maintained. It is suggested that you try DiaCanvas2 instead.
GLAME (GNU/Linux Audio Mechanics) is meant to be the GIMP of audio processing. It is designed to be a powerful, fast, stable, and easily extensible sound editor for Linux and compatible systems. It has full support for non-destructive editing including undo/redo and applying LADSPA effects. Its supported platforms are Linux, BSD, IRIX, and OS X. It uses guile and libxml, and the GNOME libs available is highly recommended. MP3 and Ogg files can be processed if libmad and libvorbisfile are installed.