BRL-CAD is a powerful constructive solid geometry solid modeling system that includes an interactive geometry editor, ray-tracing support for rendering and geometric analysis, path-tracing for realistic image synthesis, network distributed framebuffer support, and image and signal-processing tools.
Jhead is a command line driven utility for extracting digital camera settings from the Exif format files used by many digital cameras. It handles the various confusing ways these can be expressed, and displays them as F-stop, shutter speed, etc. It is also able to reduce the size of digital camera JPEGs without loss of information, by deleting integral thumbnails that digital cameras put into the Exif header. If you need to add Exif support to a program, this is a simple program to cut and paste from. Many projects, including PHP, have reused code from this utility.
lcra renames filenames like COMMAND.COM and MAIN.C to more tasteful ones like command.com and main.c. It tries to guess which filenames are DOS-ish ones needing changing, and which are really meant to be uppercase. It will fix the contents of a directory and all subdirectories. The companion program nsra changes spaces in filenames to underscores.
OSS provides sound card drivers for most popular sound cards under Linux, *BSD, Solaris, UnixWare, OpenServer, AIX, HPUX, LynxOS, VxWorks, and Tru64. These drivers support digital audio, MIDI, synthesizers, and mixers found on sound cards. These sound drivers comply with the Open Sound System API specification. OSS provides a user-friendly GUI which makes the installation of sound drivers and configuration of sound cards very simple. It supports over 200 brand name sound cards, and provides automatic sound card detection, Plug-n-Play support, support for PCI audio soundcards, and support for full duplex audio.
Pip is a wrapper for programs that won't use stdin and stdout, but require filenames to be given on the command line; it lets you use '-' as a special filename. Now you can build pipelines to your heart's content. Pip takes care of creating and removing the temporary files needed. Also included is pip_latex, which handles the peculiarities of TeX and LaTeX.
The Simple Sockets Library makes sockets easy to use and comes as public domain source code. It resembles C's file I/O, uses whatever port is available, has named servers and port reuse, streaming/blocking sockets used, polling support, blocking/selection support via numerous functions, timeout control and firewall support.