multi-platform cross assembler for 6502/6510/65816 cpu
ACME is a free cross assembler released under the GNU GPL. It can produce code for the following processors: 6502, 6510 (including illegal opcodes), 65c02 and 65816. ACME supports the standard assembler stuff like global/local/anonymous labels, offset assembly, conditional assembly and looping assembly. It can include other source files as well as binaries while assembling. Calculations can be done in integer or float mode. Oh, and it is fast.
JWasm is a Masm-compatible assembler. It supports 16-, 32- and 64-bit code, instructions up to AVX and various output formats. It's written in C.
Modern command-line cross-compiler of 8bit processor Z80(and R800) assembly language. Support many directives(even ZX-Spectrum specific as snapshot .SNA generation), has built-in Lua scripting engine, 3-pass design. Windows/DOS/FreeBSD.
NedoPC SDK is a set of development cross-tools (compilers/emulators) to develop system and user software (and hardware) for some old home minicomputers and new "homebrew" hobbyist-friendly computers (including development of that kind of computers)
BASIC Compiler and Interpreter
John's Mutant contains several projects. The current project is a Minimal BASIC compiler for Linux systems using AMD64 compatible CPUs. You can download the MinimalBASIC compiler source in the Files section.