AlbinoBlackSheep.com - Hosts lots of games and videos, features tutorials on working with Flash.
FlashKit.com - Numerous tutorials for working with Flash including step-by-step guides for certain types of games.
Kirupa.com - Extensive collection of tutorials for Flash including guides for specific types of games such as shooters.
Lassie Adventure Studio - A 2d creation image with the feel of the old style Lucasarts games.
Sploder.com - Create a Flash game from a wide range of objects and then embed it into your MySpace, Blogger, and more sites.
General Sites & Resources
Anim8or.com - A 3d modeling animation system.
byond.com - Create your own games with their tools, host them on the site, let thousands of people play.
GameDiscovery.com - Everything you need to create a game including a pool of ideas submitted by users.
Martin Piecyk's Website - A guide to learning how to make games with links to numerous resources.
VGMusic.com - A gigantic archive of video game midi files that, after asking permission from the people who made the files, you could possibly use in your own freeware games.
Visionaire2d.net - An engine to make 2d adventure games with no programming language knowledge required.
YoYoGames.com - Provides game making tools, beta testing, downloads, works in progress, a community and more.
Charas-Project.net - A character generator for use with RPG Maker.
CrankEye.com - Lots of resources for RPG Maker including character editors, soundfiles and more.
DualSolace.com - Home of the RealFeel 2D MMORPG making software.
FreeMMORPGMaker.com - Home of the Eclipse MMORPG software and also includes many resources for your games such as sprites and sounds.
PhanxGames.com - RPG making resources such as graphics, midis, and wave files. Able to upload games up to 50mb in size.
PlayerWorlds.com - A popular system for crating MMORPGs.
RPG Maker - Home of the series of the RPG Maker series of programs.
RPGCrisis.net - Downloads and tools for various RPG engines.
RPGRevolution.com - Tools and utilities for 13 different game making engines. (via)