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.

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.

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

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).

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)

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

Collection files and links to toolset for x86 assembler programming.

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 sets.