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.
MIT/GNU Scheme is an implementation of the Scheme programming language, providing an interpreter, compiler, source-code debugger, integrated Emacs-like editor, and a large runtime library. MIT/GNU Scheme is best suited to programming large applications with a rapid development cycle. Recent versions of the system are supported on the following platforms: GNU/Linux, *BSD, OS/2, and Windows.
NASM is an 80x86 assembler designed for portability and modularity. It supports a range of object file formats including Linux a.out and ELF, COFF, Microsoft 16-bit OBJ, Win32/64, and Apple Mach-O. It will also output plain binary files. Its syntax is designed to be simple and easy to understand, similar to Intel's but less complex. It supports all currently known opcodes, and has advanced macro capability. It includes a disassembler as well.
Harbour is a free, cross-platform compiler for the Xbase language. It is designed to be as compatible with CA-Clipper as humanly possible. Harbour ships with full source and makefiles, and combined with one of many C compilers will create executables which run natively on the following platforms: Linux, FreeBSD, DOS, Windows 3.x/9x/NT/W2000, and OS/2.
An almost ISO C compatible C compiler that produces binaries for 6502-based computers. Targets that are supported out of the box are: Apple ][, Atari 8-bit machines, Commodore C64/C128/C16/C116, Commodore Plus/4, Commodore 600/700, GEOS for C64, and Lynx. The package includes a complete suite of assembler development tools (assembler, linker, archiver) which allows mixing of C and assembler code.