The Advanced Bash Scripting Guide is both a reference and a tutorial on shell scripting. This comprehensive book, the equivalent of 1,000+ print pages, covers almost every aspect of shell scripting. It contains 382 profusely commented illustrative examples, a number of tables, and a cross-linked index/glossary. Not just a shell scripting tutorial, this book also provides an introduction to basic programming techniques, such as sorting and recursion. Included scripts are the Game of Life, a Perquackey variant, a Morse code trainer, and an implementation of the Gronsfeld Cipher. This book is suited for both individual study and classroom use. It covers Bash, up to and including version 4.2. Note that users of miniaturized single-board computers running Linux, such as the Raspberry Pi and the Beagle Bone, would find this Guide useful for learning and running Bash scripts to explore and expand the capabilities of these small, but powerful machines.
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.
spooky-c is a C version of Bob Jenkin's spooky hash. The only advantage over Bob's original version is that it is in C, not C++,'and comes with some test and benchmark code. This is a very competitive hash function, but is somewhat unportable (64-bit little endian only). It's more portable than some of the contenders like CityHash.
se is a screen-oriented version of the classic UNIX text editor ed. The editor implements many of the commands of ed, but instead of being line-oriented, se is screen-oriented. The command syntax is very familiar to users who already know ed. If you get stuck, there is a built-in help system that describes many of the available commands. Many configurable options can be loaded from a .serc file. se can be run interactively or in a script via the included scriptse utility. The editor is portable across many platforms, supporting major Linux and BSD distributions as well as other systems like GNU, Minix, Haiku, OpenSolaris, and Cygwin.
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.
Steel Bank Common Lisp is a development environment for Common Lisp, with excellent support for the ANSI standard: garbage collection, lexical closures, powerful macros, strong dynamic typing, incremental compilation, and the famous Common Lisp Object System (multimethods and all). It also includes many extensions, such as native threads, socket support, a statistical profiler, programmable streams, and more. These are all available through an integrated, interactive native compiler which feels like an interpreter. SBCL is unique in being a multiplatform native compiler which bootstraps itself completely from source, using a C compiler and any other ANSI Common Lisp implementation.