Will Perone

Here are some helpful tools I like to use in my projects:
Simple Directmedia Layer A nice cross platform media abstraction that provides low level access to audio, video (which has integrated opengl support), and input.
SDL Net A simple sockets networking abstraction for SDL. Makes it a little easier to get networking up and running, but it doesn't support some basic things like resolving your own ip.
SDL Image Image loading addon for SDL, will handle loading BMP, PNM (PPM/PGM/PBM), XPM, LBM, PCX, GIF, JPEG, PNG, TGA, and TIFF
SDL TTF True Type Font loading addon for SDL, for when you need to write text to screen.
OpenGL Bitmap Font Builder This program generates a bmp that is a texture of an entire font so that you can load and display text with openGL.
GLui A GLut based user interface library for rapid ui creation for openGL applications.
FMOD I never use SDL for my audio, I always use FMOD instead (and yes, it is cross platform). It supports streaming mp3/ogg/wma support, frequency domain stuff, 3d sound, midi, mods, dsp and much more.
STL Port
SGI STL documentation
The best STL implementation around. If you are still using Microsoft's broken uncompliant version of STL, tisk tisk.
Line Counter Plugin An IDE addon for Visual Studio that does all sorts of neat line count statistics on your projects.
WinTabs An IDE addon for Visual Studio that puts window tabs in to make navigating your open source windows much faster, this is especially helpful for VC 6.
Visual Assist An IDE addon for Visual Studio that adds enhanced syntax highlighting, suggestion listboxes, and all sorts of other neat things to make your IDE experience much more pleasant.
Doxygen A documentation system that helps you create automatic documentation in HTML, PDF, latex and other formats for your projects based on your codetree and source comments.
Doxbar An addin for Visual Studio to make working with doxygen just one click away.
Installer VISE Create installation wizards for your games/applications with ease.
Nullsoft NSIS Create installation wizards for your games/applications with ease.
Windows Template Library
WTL tutorials/examples
Tired of programming low level win32 API code because MFC is so convoluted? Well WTL is your solution for quickly creating awesome customizable UI's in windows.
Microsoft Platform SDK Update If you've never updated your core files for Visual Studio, chances are you are working with an outdated version of the Microsoft Windows SDK. Update it here.
Visual Studio 6 Processor Pack Adds support for today's latest processor extensions to Visual Studio 6.