C Almost Generic Library (CAGL) is a set of C macros which generates typed arrays, lists (singly or doubly-linked), hash tables, and balanced binary trees, as well as many useful functions to manipulate them. The containers grow automatically, and their memory is managed by the library. The container data, or elements, may also be managed by the library, depending on the options specified by the programmer. The aim is to free C programmers from the drudgery of implementing common data structures and algorithms. CAGL also provides some safety by making the containers typed instead of void pointers. Although, at most, two macros are invoked to declare and define a container type, manipulation of the containers is done using functions generated by the macros. A simple naming convention is used to get around the limitation that C doesn't support function overloading.
Dynace is a portable extension to the C language which adds object-oriented facilities, including classes with multiple-inheritance, a meta-object protocol, dynamic dispatching via generic functions, a garbage collector, threads, and an extensive class library, including an optional GUI library. It has complete documentation and a tutorial.
s6-networking is a collection of small Unix tools designed to help networking. It includes clock synchronization, Unix and TCP super-servers, Unix and TCP access control, and other miscellaneous utilities. It is particularly suited for management of clients and servers on embedded devices, but works just as well on larger systems.
s6-dns is a small, efficient, complete, and IPv6-ready DNS client library, with synchronous as well as asynchronous APIs. It is designed to replace libresolv in projects that need to perform DNS resolution. It also comes with small command-line utilities to make common and not so common DNS queries.
cconstants is a library and a set of commandline utilities which allow the values of constants defined in C header files to be queried outside the C preprocessor. This allows the values of these constants to be queried from programming languages other than C, on systems without the C preprocessor installed, and on systems on which the header files defining these constants are not available.
snappy-c is a C port of the google snappy compressor (http://code.google.com/p/snappy/). The compressor is very fast with a reasonable compression ratio. It is mainly useful for projects that cannot integrate C++ code, but want snappy. It also contains a command line tool, a benchmark, random test code, and a fuzz tester. The compression code supports scather-gather and linear buffers. The scather gather code is ifdefed (-DSG) and can be removed with unifdef.