zlib is designed to be a free, general-purpose, legally unencumbered, lossless data-compression library for use on virtually any computer hardware and operating system. The zlib data format is itself portable across platforms. Unlike the LZW compression method used in Unix compress(1), the compression method currently used in zlib essentially never expands the data. (LZW can double or triple the file size in extreme cases.) zlib's memory footprint is also independent of the input data and can be reduced, if necessary, at some cost in compression.
di is a disk information utility that displays everything that df does and more. It features the ability to display your disk usage in whatever format you prefer. It also checks the user and group quotas, so that the user sees the space available for their use, not the system wide disk space. It is designed to be highly portable across many platforms and is great for heterogenous networks.
CUT is a unit-testing framework for C, C++, and Objective-C. Unlike other unit testing tools, CUT doesn't strive to be an SUnit clone. It automates a lot of the drudge work often encountered when using other unit testing packages for the C family of programming languages. CUT may also be used to unit-test assembly language software in some circumstances.
SIMD Cross-platform headers is a cross- platform, cross-compiler, cross CPU C/C++ header collection that aids the creation portable vectorized (SIMD) C/C++ code. It supports (or partially supports) x86 (MMX/SSE/SSE2) GCC and MSVC, PPC Altivec GCC and CodeWarrior, ARM GCC, and software-emulated SIMD.
glbmp is a lightweight and portable partial glaux replacement, providing auxDIBImageLoad and related device-independent bitmap image loading functionality. At the basic level, it's a flexible bitmap loader and decoder that can be used anywhere the color data of a bitmap is required. It supports uncompressed monochrome, 16 color, 256 color, and 24-bit bitmap files of any size, and allows for flexible output formats.
Adime is a library for constructing Allegro GUI dialogs in a way similar to scanf(), using a format string. Other features include a (customizable) 3d look and feel, 3d versions of some of Allegro's GUI procs, complete help in many formats (HTML, txt, chm, texinfo, man, devhelp, and RTF), and four example programs. Adime can currently be compiled on Linux, Windows/MinGW32, Windows/Borland C++, Windows/MSVC, DOS/DJGPP, DOS/Watcom, Apple MacOS X, and QNX.
Nickel is a library for hierarchical maps and .ini files. It can be used to easily read, manipulate, and write configuration data in .ini format, among other things. It's also handy wherever a map structure (or tree of maps) is called for. Nickel focuses on speed, robustness, and portability.