3D Map Realm: Reviews of Quake 2, Half-Life and Unreal single player maps. Also provides testing services and a discussion forum.
Cooltech Games: Patches and modifications for Half-Life, Unreal Tournament, and Quake.
Crosshair Central: Provides crosshairs for Central, Quake 2, Half-Life, Counter-Strike, Sin, and Kingpin, tools, and tutorials.
DAV Levels: Levels and maps for Doom2, Heretic, Hexen, Half-Life, Quake and Quake2.
Foyleman: Soldier of Fortune, Serious Sam, and Return to Castle Wolfenstein.
Garjen Software: Add-ons, custom levels and utilities for games such as Duke Nukem 3D, Wolfenstein, and Lemmings.
Grey Fusion: Tips and ideas for editing game engines for Half-Life, the Quake Series, Red Faction, and the Unreal Series.
M Planet: Includes mapping and level editing instructions, and downloads.
Mirage's Maps: Maps for Half-Life and Quake 3.
PC Game Mods: Maps and modifications. Covers Star Wars games, Doom 3, Half-Life 2, Enemy-Territory and Quake 3.
Poly Count: Includes downloads, modifications and game resources.
Slacker's House: Unreal Tournament, Unreal Tournament 2003, and Quake 3 maps.
Super Capture the Flag: Includes game modifications, downloads and information. Plays on Quake and Half-Life.
The Bullseye Crosshair Collection: Includes modifications for the Quake Series and Half-Life.
The Mastahuka Page: Offers maps for games including Half Life, Unreal Tournament and Blood.
Total Conversions.com: Deals with modifications to games developed by 3DRealms.
Ultimate Mapping: Maps for Counter Strike and Battlefield 1942.
Vondur's War Supply: Includes custom maps for Quake, Quake2, Quake 3 Arena and Half-Life.
VR21: Offers modifications and add-ons for several games, including Doom and Quake.
Wavelength: Focuses on editing and game modification in Half Life, Quake and Unreal series games. Includes downloads, tutorials and utility downloads.