Microsoft Macro-Assembler is now free, although you have to have Visual C++ 2005 Express Edition installed on your Win2000/WinXP SP2 or Windows Server 2003 computer and it is limited to non-commercial uses by license.
The Netwide Assembler v0.98, a free protable downloadable assembler for the Intel 80x86 mircroprocessor series, which uses the traditional INtel instruction mnemonics and syntax. Free download.
MASM32 is a working development environment for programmers who want to write 32 bit Microsoft Assembler (MASM).
Assembly language IDE for programming with MASM. It is a Win32 program and was written totally in ASM. It features syntax highlighting, a customizable Tools menu, project wizards, addin components to extend and add features, and the familiar multiple do
If you are interested in 32-bit programming for Windows 95/98/ME/NT/2000/XP using assembler, you will find everything you need here including an Assembler, Resource Compiler, Linker, Symbolic Debugger, Editor, Help Compiler, Information, Tutorials, Sample
CodeX Assembler is a Freeware assembler for x86 platforms that supports in the current version 1.0 and version 2.34 of the Opcode Map the instruction sets of all Intel CPUs up to the Pentium IV as well as the AMD 3D.
High Level Assembler (HLA)
The High Level Assembler (HLA) is a 32-bit 80x86 assembly language that is portable between Win32, Linux, and FreeBSD.
NewBasic Assembler (NBASM)
The NewBasic Assembler, NBASM, is an x86 assembler and is near MASM 5.1x compatible. NBASM is intended for use by beginners starting to learn assembly.
QLINK is a DOS linker and analysis tool designed to link together MS-DOS compatible .OBJ files. According to the website it can replace the MS-DOS LINK.EXE program when producing MS-DOS compatible .EXE and .COM files.
The Bottom-Up Assembler for ReactOS includes an assembler, a disassembler, debugger and ide.
The flat assembler is a fast and efficient self-assembling 80x86 assembler for DOS, Windows and Linux operating systems. Currently it supports all 8086-80486/Pentium instructions with MMX, SSE, SSE2, SSE3 and 3DNow! extensions, can produce output in binary, MZ, PE, COFF or ELF format. The flat assembler is self-compilable and the full source code is included.
Assembly Studio (IDE)
Full IDE for x86 Assembly Language Programming, featuring TASM/TASM32 support. Designed for Windows XP/2K/NT.
A cross macro assembler that assembles code for the 680xx using a PC.