Play chess online, learn new chess strategies, tactics and rules, study chess games and openings, all for free.
http://www.chess.com/

A guide to hundreds of party game ideas sorted by theme or occasion.
http://www.party411.com/gameguide.html

Developed by Epic Games, the Unreal Engine was first used in the shooter game "Unreal", in 1998. It is mainly used for first person shooter games.
http://udn.epicgames.com/

Open Dynamics Engine (ODE) is an open source physics engine for simulating rigid body dynamics, licensed under the BSD license and LGPL.
http://www.ode.org/

Endorphin is the first dynamic motion synthesis software, combining physics, AI and genetic algorithms. It is used in movies and games. NaturalMotion, the developer of endorphin, offers a free version of the software (eLE 2.7) for learning purposes and evaluation.
http://www.naturalmotion.com/endorphin.htm

Another middleware physics engine for computer and video games, available to game developers. Sony has licensed PhysX for their Playstation 3 console.
http://www.ageia.com/physx/

Havok Game Dynamics SDK (or just "Havok") is a middleware physics engine created for computer and video games. The Havok source code can be licensed, and has been used for over 100 well-known video and computer games.
http://www.havok.com/

Based in Vienna, Austria, PepFX specializes in custom online games, specifically in Flash and Shockwave game creation.
http://www.pepfx.com/

Everything about Mac games, game trailers, ratings and hardware.
http://www.apple.com/games/

Yahoo Games is the section of Yahoo! in which members can play games with each other or by themselves. The games are either Java applets or require a program to be downloaded.
http://games.yahoo.com/