September 27, 1999 - Luke Hodorowicz
This article explains how to convert WorldCraft map files into your own format so that you don't need to write your own level editor.
zLib compression is free to use. It is used as default compression in PNG. Can also be used to pack/unpack .zip and .gz files.
WAVE file format
This is a description of the file format for .wav files.
ZIP file format
This is the file format for PKWare's .zip files.
This article explains the MPQ format as used by Blizzard's Diablo and Starcraft. It also happens to explain a very good hashing algorithm used in the MPQ archives for determining file position.
The zLib home page
This programming library provides very good compression and is quite easy to use.
Information on file formats and extensions.
How to parse .X files
Sep, 2001 - Jim Adams
Shows how to parse X files using DirectX 8, but not the D3DX utility library.
An In-Depth Look into the Win32 Portable Executable File Format
Feb, 2002 - Matt Pietrek
This article gives a detailed explanation of the Windows Portable Executable file format.
Loading and displaying .X files without DirectX
Mar, 2005 - Paul Coppens
A detailed explanation of the X file format used by DirectX for 3D models.
The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!)
Oct, 2003 - Joel Spolsky
This article gives a very good (and humorous) introduction to Unicode.
WikiPedia explains how UTF-8 unicode encoding works.
UTF-16 / UCS-2
Wikipedia explains how UTF-16 and UCS-2 unicode encoding works.
Collada is an open standard for exchanging 3D media in XML format.