Official Intel Architecture Optimizations Manual, Intel Architecture Software Developer's Manual, Pentium Processor Family Developer's Manual.

Short overview containing all instructions (transfer, arithmetic, logic, jumps), a diagram of the registers (EAX, EDX, ECX, EBX), demo program, fits to one single page, download, free

Covers MASM, TASM, NASM used with Win32, DirectX, multimedia. Especially for Games and Demos. Has sample code.

A quick reference list of DOS interrupts has been extracted from a large list compiled by Ralf Brown.

The various forms of A20 gate control.

Very informative docs and tutorials (zip, html) on 3d programming, assembly.

For the comp.lang.asm.x86 and alt.lang.asm newsgroups.

List of most Mnemonics for x86 with description.

Tutorial written by Gavin Estey.

Detailed step by step tutorial.