Chump is a table-driven assembler and dissembler with a very fast new architecture input format. Both the assembler and disassembler are created using a single description. It comes with descriptions for ARM, MIPS, Stump, and 6809. It is intended for use as a library compiled with other programs to allow line assembly and disassembly.
Flat Assembler is a fast and efficient self-assembling 80x86 assembler. It supports x86 and x86-64 instruction sets with MMX, 3DNow!, SSE up to SSE4, AVX, AVX2, and XOP extensions. It can produce output in binary, MZ, PE, COFF, or ELF format. It includes powerful but easy-to-use macroinstruction support and does multiple passes to optimize the instruction codes for size. It is written entirely in assembly language.