One of the most important things for the programmers to develop is to keep a good list of useful sites, where additional information and other links can be found. Here goes my collection of nice links.
 

Name: Programmer's Heaven
URL: http://www.programmersheaven.com
Description: Quite a large site, containing loads of sources and programs about many programming languages. Also offers CDs with the contents of the web site.

Name: WDOSX - Wuschel's DOS Extender
URL: http://www.wuschel.demon.co.uk
Description: The home page of the best DOS Extender currently around. Features PE emulation under DOS! Also supports EXE, LE and RDOFF binary formats. Check the page for updates.

Name: Ralf Brown's interrupt list
URL: http://www.ctyme.com/rbrown.htm
Description: Very important source of information for every serious DOS programmer.

Name: John Fine's homepage
URL: http://users.erols.com/johnfine/
Description: The owner of that web site is also a contributer to the NASM project. On the site you can find some prereleases of NASM. Also lots of stuff about protected mode as well as some interesting sources are available.

Name: Assembly gems
URL: http://www.df.lth.se/~john_e/gems.html
Description: Contains many gems for assembler. Also has some stuff about assembler and Motorolla.

Name: Protected mode basics
URL: http://www.x86.org/articles/pmbasics/
Description: Strongly recommended for beginners. Contains many diagrams, tables and detailed description of how the protected mode works. Also has routines for entering and exiting protected mode.

Name: Paul Hsieh's x86 assembly page
URL: http://www.geocities.com/SiliconValley/9498/asm.html
Description: Mainly contains usefull artices.

Name: Whiz kid technomagic
URL: http://www.geocities.com/SiliconValley/Heights/7394/
Description: This page looks quite stupid at the beginning but take a look at it - it contains some very usefull assembler sources and documentations. Just ignore the design of the web site :)))

Name: GazTek website
URL: http://members.xoom.com/gaztek/
Description: The owner of the site has developed several programs that are available on the web page, such as: HTTP server, 32 bit assembler, operating system (early stage of development). Also has a page dedicated specifically to OS programming and development.

Name: Macro libary for mixed programming
URL: http://www.dnaent.com/2.htm
Description: Explains how to do mixed C and assembly programming.

Name: Assembly language and graphics programming
URL: http://www.rbthomas.freeserve.co.uk/
Description: This site looks like very promising one. It is currently not very rich on resources but contains some useful docs as well as very rare sources. Hopefully it will grow more in the future.

Name: g f x
URL: http://www.scs.ryerson.ca/h2jang/gfx_c.html
Description: Many documents explaining how to do different effects in graphics programming. Also covers DirectX and OpenGL

Name: 3D engines list
URL: http://cg.cs.tu-berlin.de/~ki/engines.html
Description: The most comprehensive list of 3D engines on the net. The site includes nice features, such as listing the engines by your criteria, i.e. programming language, targeted OS, etc.

Name: Graphics programming
URL: http://www.vis.colostate.edu/~scriven/Yamaha/Coding.html
Description: Site mainly concentrated on graphics programming but also contains other issues such as: serial/modem programming, optimisation and CPU information and other interesting things like new keyboard layout.

Name: Delphi GUI
URL: http://pagina.de/delphigui/
Description: Graphic library written in Delphi but targeted for DOS, using WDOSX. Also makes possible to write Delphi GUI applications and run them under DOS.

Name: MP3 Tech
URL: http://www.mp3tech.org/
Description: Documentations, players, sources.... everything about the MPEG1, layer 2 and 3 file formats.

Name: Game programming '99
URL: http://www.gameprog.com/
Description: Covers many topics on game programming, such as: graphics, sound, effects, physics, AI, etc. Also contains information on DirectX and OpenGL.

Name: Floating point's game developers jumpsite
URL: http://www.ben2.ucla.edu/~permadi/gamelink/gamelink.html
Description: WOW! You will need several days to go through all these links. If you aren't really looking for anything particular but just hoping to find good sites about programming - start here.

Name: Programmer's virtual library
URL: http://www.strangecreations.com/library/index.htm
Description: Contains tutorials, docs and FAQs on the following topics: games programming, assembly language, sound and music, graphics, hardware, etc. Also has a very long list of little routines and sources for different needs.

Name: Secrect's Dox page
URL: http://www.nauticom.net/www/secret/Dox/
Descrption: Various topics are covered on this site, including: SVGA tutor, CMOS, fixed point math, introduction to 3D, protected mode basics, keyboard/joystick/mouse information and even Win32 programming.

Name: Epsilon coder page
URL: http://www.cs.pdx.edu/~idr/
Description: Not very good web site but has few good articles about compression and graphics programming.

Name: The Dark Corner BBS fileareas
URL: http://www.dc.ee:80/Files/
Description: Contains many source codes and docs about programming in different programming languages.

Name: Operating Systems on the web
URL: http://www.osweb.8m.com/
Description: This site contains resources about OS programming and has links to a large number of OS projects. This should be obviously your starting point if you would like to develop your own OS.

Name: Protected mode and operating systems
URL: http://www.execpc.com/~geezer/os/
Description: Well structured web page covering topics mainly about protected mode and its realisation in the operating systems. Has some nice source code as well. DOS & Linux are explained (not in details though).
Name: Advanced programming languages

Name: OS theory page
URL: http://home.c2i.net/tkjoerne/os/index.htm
Description: Another page with information about writing operating systems. Opposing to the name of the page, there are actually sources available on the page, such as boot loader, FAT12 and FAT16 routines, etc.

Name: Advanced programming languages
URL: http://lsi.uniovi.es/~labra/APL.html
Description: A big site concentrating on programming languages and especially their design. If you have interest on that topic you will definately like this site.

Name: Java VM specification
URL: http://www.s2.org/s2/vmspec/VMSpecTOC.doc.html
Description: Detailed information on the JAVA virtual machine.

Name: Windows 95 assembly language programming
URL: http://www.eskimo.com/~htak/win95asm/win95asm.htm
Description: Explains how to program under Win32 with examples. TASM 4.0 used for the examples.

Name: Iczelion's Win32 assembly homepage
URL: http://members.xoom.com/Iczel/
Description: The best site on Win32 and assembly programming. Covers broad range of topics together with examples.

Name: PHG opcodes list
URL: http://www.chat.ru/~phg/
Description: Mainly concentrates on some undocumented or odd instructions available. Contains the opcodes for MMX 2!!

Name: sandpile.org
URL: http://www.sandpile.org/
Description: Everything you will need to know about the IA-32 (x86) architecture.

Name: The programmer's file format collection
URL: http://www.wotsit.org/
Description: If you can't find the description of a particular file format on that site, than probably there isn't such a documentation available :))

Name: The graphics file formats page
URL: http://www.dcs.ed.ac.uk/%7Emxr/gfx/
Description: Another page with file descriptions but just graphic ones. Much smaller compared to wotsit.org, but it covers the 2D/3D graphics file formats very well.