There are hundreds of programmer's sites so I have concentrated on those sites which will be helpful to Win32 assembler programmers. I regularly check out all the sites listed here. I do not link to sites containing unfinished programs, and I only include links to sites which I regard as exceptional.
Wayne J. Radburn's assembler page Learning from one of the pioneers of Win32+assembler. Includes his famous skeleton sample code, and two very useful tools. There is PEView, which enables you to view the internals of exe, dlls, sys, obj, lib and dbg files and thINC which converts Windows "h" files to include files for use with an assembler.
Donkey's stable A visit to this site will be well rewarded for all assembler programmers. Here you can find Toolbar Paint, an excellent image list paint package targeted directly at programmers who want to design their own toolbar graphics. Res2Dlg a resource extractor, various add-ins for the Radasm IDE, a large collection of code libraries with source code, include files, and GoAsm samples and projects.
Iczelion's Page Large resource centre for asm + Win32, largely MASM orientated, but with the aim of promoting Win32 + asm. Many links and files, and a most useful and growing list of tutorials. A must visit if you are interested in this subject.
Randall Hyde's WEBster Page Excellent resource centre for the serious assembler programmer, put together by the author of "The Art of Assembly Language Programming" and of the HLA assembler.
Programmers' Heaven Almost 30,000 files 1,700 links covering all aspects of programming.
René Tournois RosAasm site. And now for something completely different. René has completely broken the mould by making an executable-maker. Just enter the source and produce the Win32 executable! An immense amount of hard work has also resulted in much useful information on this site.
T. Schütz's page Great fun and different - see a new angle to Win32 + assembler and lots of regularly updated links.
Dolphinz Win32 assembler page Tasm based tutorials and examples.
Kaproncai Tamás' page A well maintained and nicely put together collection of materials and links.
NL Software's Freebyte site Up-to-date links to and information about free tools for the programmer.
The Free Country Another well-maintained and attractive site containing links to free tools for the programmer, and includes recommended books, sources of information etc. Maintained by Christopher Heng.
Assembly Programming Journal An online journal for assembler programmers generally, often with articles about Win32 programming (archive).
Mammon's Assembly page Lots of original material and links in a well maintained site.
Hutch's Assembly page This page has some useful links, programs and information.