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.
avrLab tries to be an complete IDE for the AVR microcontroller chips from Atmel. It offers an editor with syntax highlighting which has standard editor commands like copy, cut, paste, goto line, search, and replace. Additionally, it includes support for tavrasm (a compiler for the AVR assembly language), uisp (used for the communication to the AVR), and much more.
masmz80 is a very lightweight assembler for the Zilog Z80 processor. Objects generated contain information about global symbols, unreferenced symbols, and sections that need to be relocated, so it's easy to write code in many files and reference one project files' symbols from another. Linking these objects using included mlinkz80 produces an image ready for burning on an (E)EPROM.
asfpga is an assembler written for use in FPGA design. It can be easily modified for a particular instruction set. The ultimate goal of this software is to allow a FPGA designer to easily write assembly code for a custom instruction set. The current version allows you to create a listing file, a memory dump file which can be used in debugging HDL code using $readmemh() or equivalent routine, and a binary file which can be used to program an EPROM.
Yasm is a complete rewrite of the NASM assembler. It currently supports the x86 and AMD64 instruction sets, accepts NASM and GAS assembler syntaxes, outputs binary, ELF32, ELF64, COFF, Mach-O (32 and 64), RDOFF2, Win32, and Win64 object formats, and generates source debugging information in STABS, DWARF 2, and CodeView 8 formats.
Aasm is an advanced modular assembler designed to support several target architectures. It has been designed to be easily extended. Its global architecture takes advantages of dynamic libraries to provide input, assembler and output modules. The input module supports Intel syntax (like nasm, tasm, masm, etc.). The x86 assembler module supports all opcodes up to P6 including MMX, SSE and 3DNow! extensions. F-CPU and SPARC assembler modules are under development. Several output modules are available for ELF, COFF, IntelHex, and raw binary formats. Advanced features include symbol scopes, an expressions engine, big integer support, macro capability, and numerous and accurate warning messages (over 300).