Brace is a dialect of C that looks like Python. It has coroutines, hygenic macros, header generation, and libraries with graphics and sound. It is meant to be good for beginners, kids, and experts. Brace is translated to C, then compiled, with #! support and cached executables. It is fairly portable, and runs on GNU/Linux, Unix, and Windows with MinGW. It should also run on Mac OS X. It comes with a lot of demo programs, many with animated graphics.
Minnow is a concurrent programming language with a Ruby-like syntax. It compiles to an executable and uses a companion library to allow fully-rebalanced microthreads. Minnow gains a lot of strength from its actor model, which uses message passing, as opposed to threads and locking, as its concurrency model. Taking a cue from Erlang, actor creation and message passing is extremely lightweight (often on the order of a few nanoseconds). The language has a built-in foreign function interface that allows developers to leverage existing C-based libraries in a simple SWIG-like manner. Minnow's object model is based on "melding" features together to form objects.
X# (pronounced X-sharp) is an XML-oriented programming language designed to quickly create Web applications and services. Everything is represented as an XML tree, and instead of using functions to manipulate information or perform actions, all possible operations are done by adding, removing, or changing nodes from this tree. Since there are no functions to learn and everything is done intuitively, even inexperienced developers can create complex Web applications and services quickly.
Open Watcom consists of the famous Watcom C++ and WATFOR compilers -- now open source. Open Watcom is mainly used for developing embedded, DOS, and ncurses software. Open Watcom includes the C/C++/Fortran IDE from Watcom for DOS and a full set of command-line tools for compilation, including the superb Watcom debugger. Open Watcom emits easy-to-understand errors and warnings when things go wrong. Open Watcom generates small statically linked binaries for Linux, Win32, Win16, OS/2, QNX, NetWare, and MS-DOS real and protected mode, among other targets. However, Open Watcom is still only beta-quality on Linux and BSD. The two most serious issues are imperfect C++ template support and an inability to dynamically link with shared libraries built by GCC. Also, Open Watcom is released under the Sybase Open Watcom Public License, which is considered non-free by most Debian Linux developers. NOTE: Open Watcom binaries for Linux are not available anywhere. You must build it yourself. 1.5 has known build issues on Linux; use version 1.4 or the current daily build instead.
nwcc is a C compiler for Unix systems. It targets Linux, Mac OS X, BSD, and Solaris on 80x86 (with nasm and gas), Linux, Mac OS X, and FreeBSD on AMD64 (with yasm and gas), Solaris and Linux on SPARC (64-bit), AIX and Linux on PowerPC (32- and 64-bit), and IRIX on MIPS (64-bit). Cross-compilation is also supported. It doesn't feature any software development support beyond plain compilation.