Windows API reference
Description of Windows API functions.
Linux kernel syscalls reference
Description of linux syscalls, with includes for FASM and gas.
Single Unix Specification v3
POSIX standard for unix-based operating systems. Includes libc reference.
General-purpose assembler for both win32 and linux. Can include FASMLIB by sources, and produce executable directly without any linking.
Win32-only commercial assembler with lot of license restrictions. Most popular assembler on win32 platform.
General-purpose assembler for both win32 and linux. It's development has been resumed recently, but it is still inferior to YASM.
This is NASM clone, with additional features (64 bit support etc.). Usage of FASMLIB in NASM and YASM is exactly same. Unlike NASM, this project is under development.