An 80x86 assembler designed for portability and modularity. [Open source, LGPL]

A complete rewrite of the NASM assembler under BSD License. is designed from the ground up to allow for multiple assembler syntaxes to be supported (eg, NASM, TASM, GAS, etc.) in addition to multiple output object formats and even multiple instruction...

An assembly language developed by Randall Hyde which can use high-level language constructs to aid x86 assembly programmer beginners and advanced assembly developers alike. (Wikipedia article)

A self-assembling open-source 80x86 assembler for DOS, Windows and Linux. It supports all 8086-80486/Pentium instructions with MMX, SSE, SSE2 and 3DNow! extensions, can produce output in binary, MZ, PE, COFF or ELF format.

Visual assembly language RAD IDE with built-in FASM assembler. Designed for easy development of big assembly written applications. Self-contained, Fresh is written in Fresh and is fully compatible with FlatAssembler (FASM).

Lists assemblers, cross-assemblers, linkers, and librarians, where available, for a wide variety of operating systems and processors.

Information and tools for Windows assembly language programming.

A86: high quality assembler, for x86 processors. D86: screen-oriented program to troubleshoot buggy programs written for DOS; freezes program states, shows values of registers, flags, memory; single steps forward or back. Eric Isaacson Software.

Linker for DOS, Windows. Open source, Artistic License.

Easy-to-use assembler for DOS and the Intel x86 and compatible processors, including support for real mode and protected mode.