MBase is a .NET-oriented meta-programming framework. It is designed for rapid development and high quality implementation of custom programming language compilers, but can also serve as a robust and flexible embeddable scripting engine. Applications are not limited to .NET platform, since MBase can be used to implement compilers targeting other platforms - JVM, native assembly, C, etc.
mdocml is a suite of tools for compiling "-mdoc", the roff macro package of choice for BSD manual pages, and "-man", the predominant historical package for UNIX manuals. The mission of mdocml is to deprecate groff, the GNU roff implementation, for displaying -mdoc pages whilst providing token support for -man.
Deva is a programming language that is small, dynamic, and has some similarities to C and Python. It is designed for embedding in C++ applications, and is also suitable for basic programming tasks. It is written to be as simple as possible, but no simpler. Deva is a multi-paradigm language: it is essentially procedural and imperative, but with support for basic functional and object-oriented idioms.
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.
FreeForth is a small and fast interactive compiler composed of an extensible set of macros generating inline compact i386 native code, including floating-point instructions, and an easy interface to Linux and Windows dynamic libraries. It uses two stacks to pass subroutines arguments and results separately from return addresses, like other Forth dialects, but unlike them, it is a simpler pure compiler (without an interpreter) offering interactivity through "anonymous" subroutines which are executed by their closing ";" macro. FreeForth is fully documented by 100K of interactive online help. Since its first release in 2006, it has been used every day for cross-development of realtime industrial applications embedded in microcontrollers, and for PC-controlled manufacturing test benches. The FreeForth distribution includes an interactive incremental assembler for the MSP430 microcontroller family.
Rhope is a dynamically typed dataflow programming language that also borrows some ideas from other paradigms. Unlike mainstream programming languages, statements are not necessarily executed in the order they are written, but instead based on their dependencies. Statements that do not share dependencies run in parallel. Most operations have value semantics (i.e. modifying an object makes a copy rather than changing the original) making this parallelism safe. For managing global state, Rhope has a transaction mechanism.
allspice is a set of Java libraries that allow you to define and implement a language that runs on top of the JVM. The packages define a YACC-like grammar and an underlying high level programming abstraction. One need never know about JVM internals to implement a new language. In addition, these compilations can be "on the fly". You can compile and execute without an intermediate class file.