Allegro is a multi-platform game library for C/C++ developers that provides many functions for graphics, sounds, player input (keyboard, mouse, and joystick), and timers. It also provides fixed and floating point mathematical functions, 3D functions, file management functions, compressed datafile, and a GUI.
DeuTex is a wad composer for Doom, Heretic, Hexen and Strife. It can be used to extract the lumps of a wad and save them as individual files. Conversely, it can also build a wad from separate files. When extracting a lump to a file, it does not just copy the raw data, it converts it to an appropriate format (such as PPM for graphics, .au for samples, etc.). When it reads files for inclusion in pwads, it does the necessary reciprocal conversions. In addition, DeuTex has functions such as merging wads, etc.
Glt is a library of C++ classes and routines for programming interactive 3D graphics with OpenGL. The aim of Glt is to augment the OpenGL API with convenient mechanisms for manipulating the OpenGL state machine. Glt is a work in progress, and by no means covers the entire OpenGL specification. However, it already includes several useful classes and is designed so that additional classes can be added easily. In addition to Glt, the GlutMaster classes provide C++ wrappers for the GLUT API.
kmamu is a shell script which installs X icons for xmame into a folder on your KDE1 or KDE2/3 desktop. (These icons can be downloaded from the homepage.) When installed, each icon has a long description name as provided by xmame -listgames, and when clicked it will launch xmame with the appropriate game. Although the install script is specific for KDE, the icons are stored in X pixmap format and can be used with any window manager.
PLIB is a set of libraries to write games and other realtime interactive applications that are 100% portable across a wide range of hardware and operating systems. It's used by Majik3D, FlightGear, and others, and includes libraries for GUI widgets, sound replay, geometry, scene graph, joystick, and fonts/text.
PPM is yet another Game Boy (Color) tile and map editor that uses GTK. It supports many export formats (raw binary, GBDK .c, ISAS .asm, TASM .asm, WLA .asm, and RGBDS .asm), and has different Game Boy Color color emulation modes. It can also import GBTD and GBMB (popular tile and map editors for Windows) files. All mouse buttons draw, and there are loads of keyboard shortcuts. It can also optionally emulate the Game Boy's display.