Gforth is a fast and portable implementation of the ANS Forth language. It works nicely with the Emacs editor, offers some nice features such as input completion and history and a powerful locals facility, and it even has (the beginnings of) a manual. Gforth employs traditional implementation techniques: its inner innerpreter is indirect or direct threaded. Gforth runs under Unix, Win95, OS/2, and DOS and should not be hard to port to other systems supported by GCC.
GNU libmicrohttpd is a small C library for embedding HTTP server functionality into other applications. It is reentrant, fast, supports HTTP 1.1, and permits listening on multiple ports. The API is simple and still powerful enough to allow programmers to use the entire HTTP feature set. SSL/TLS support is available as an option.
hamsterdb Embedded Storage is an embedded database engine written in ANSI-C. It includes B+Trees with variable length keys and records. It supports in-memory databases and endian-independent files, database cursors, multiple databases in one file, "record number" databases, and duplicate keys. hamsterdb is very fast and highly configurable. It compiles and runs on Unix platforms, Linux, Microsoft Windows, and Windows CE.
Bigloo is an implementation of the Scheme programming language. It relies on an optimizing compiler from Scheme to C. Bigloo enables connections between Scheme code and C code. It proposes many extensions to Scheme such as a regular parser compiler, an lalr parser compiler, pattern matching, an object layer, etc.
Stunnix CXX-Obfus is a code obfuscator for C and C++ source code. It converts source code into highly a mangled form, making it extremely difficult for competitors or customers to study, analyze, reuse, and re-work, while fully retaining functionality of the original code. It has many options to control all aspects of code hiding, and has full support for all syntax constructs. It is designed for multi-file projects with mixed C and C++ source and arbitrary heavy use of the C preprocessor. It includes advanced tools to exclude API symbols from mangling.
The "Schily" Tool Box is a set of tools written or managed by Jörg Schilling. It includes programs like: cdrecord, cdda2wav, readcd, mkisofs, smake, bsh, btcflash, calc, calltree, change, compare, count, cpp (K&R original), devdump, hdump, isodebug, isodump, isoinfo, isovfy, label, mt, p, patch, sccs, scgcheck, scpio, sdd, sfind, sformat, smake, sh (Bourne Shell), star, star_sym, suntar, gnutar, tartest, termcap, and ved.
Curie is a very minimalistic, tiny C library. It supports basic I/O, basic networking, S-expression based I/O, signal handling, process handling, and I/O multiplexing. If the target architecture is explicitly supported, statically linked binaries may be as small as 4-20 kilobytes; if not, then it only relies on the host's C library. The library explicitly does not provide a POSIX interface so that it may be used in conjunction with a regular host libc (or without one).