Tools - You won't get far without these ;)(Confused? Skip ahead...) MASM - Microsoft's offerings, They argue this is still supported. This or the next, your choice.
Hutch's Masm32 package- 32bit Macro Assembler compatible with Microsoft's ML.exe supplied with VC
NASM - The famous Netwide Assembler
YASM - Homepage of YASM & Libyasm, The modular assembler project
TASM - Borland's Turbo assembler.
NBASM - NewBasic Assembler for DOS. Near compatible with MASM 5.1
FASM - Flat Assembler, a relatively new entry
Emu8086 - A very good emulator/assembler, especially for beginners. Definitly worth whatever they charge you now
Alink - Alink linker, needed for linking object files & libaries. A must if you don't already have one. Note a linker is packaged with both Masm32 & VC(a dependancy for MASM).
OllyDbg - An excellent debugger, definitely the best you can get without parting with any money.
IDA Pro disassembler & debugger - An expensive bit of kit, has a good reputation, although haven't used it myself. There is a freeware version floating about although it is no longer hosted by them.
RadAsm IDE - A very good IDE with syntax highlighting for many flavours of assembly as well as some HLLs.
NasmIDE - NasmIDE and NasmEdit, download them here.

Tutorials - Next port of call: get to grips with assembly Quick guide to the basics - Confused by that? Read my quick guide to the basics
Art of (HL)Assembly (dos/win/linux) - If you only read one book/tutorial on assembly, make this it.
PC assembly tutorial - A lower level alternative to AoA, NASM syntax
General look at assembly languages - A general and detailed examination of assembly language.
Wikibook:x86 Assembly - As of now 25% complete, has a good comparison of some different assemblers if you're spoilt for choice.
(16-bit)Assembly Tutorial - I've included this because of its concise introduction to some of the theory behind assembly programming.
Assembly Language Tutor - Nice introductory text, TASM syntax
Gavin's Guide to x86 Assembly - Well structured guide, TASM syntax, covers DOS interrupts nicely
Assembly Lab - Paul Hsieh's Assembly Lab

Microsoft Specific - Want to learn to use the Win API? Microsofts' Platform SDK - Useful Development Kit for anyone using the windows API, contains invaluable documentation and libaries
Iczelion's Win32 Assembly Tutorials - No doubt the best tutorials on the subject. Bookmark it. Twice.
Win32 Assembler Coding Tutorial - 5 part tutorial, examples included. NASM alternative to above.
Win32NASM - Samples, include files and tools for Win32 programming with NASM
Windows DDK - Driver development kit for windows
Windows API reference - MSDN online reference
Win32 NASM Tutorial - Short tutorial, NASM syntax

Furthur Reading/References - What next? AMD Technical Documents - Documantation for AMD processes/chipsets
Intel 64/IA32 Developers Manuals - Straight from the dragons mouth, know your environment
Reversing:Secrets of Reverse Engineering(book) by Eldad Eilam - With malware an increasing issue, RE is as always a useful skill
Reversing School - Nice 4 part lessons by eT
Introduction to Reverse Engineering - 12 chapters introducting RE.
AsmSource - Need inspiration? Loads of examples here
More examples - Few more Win32 examples, using MASM.
Even more examples - Learn by example.
AsmCommunity - Need help? Want to join/start a project?
LANAKI's Crypto Lessons - Classical cryptography course by Lanaki