Open Watcom Assembler or WASM is an x86 assembler produced by Watcom, based on the Watcom Assembler found in Watcom C/C++ compiler and Watcom FORTRAN 77. Further development is being done on the 32- and 64-bit JWASM project, which more closely matches the syntax of Microsoft's assembler.
There are experimental assemblers for PowerPC, Alpha AXP, and MIPS.