DAV Levels
Levels and maps for Doom2, Heretic, Hexen, Half-Life, Quake and Quake2.

3D Map Realm
Reviews of Quake 2, Half-Life and Unreal single player maps. Also provides testing services and a discussion forum.

Mod Pages Network
Modification downloads and reviews for games including Half-Life, Unreal Tournament, Quake II and III, Rainbow Six, and Rogue Spear.

Mirage's Maps
Maps for Half-Life and Quake 3.

Grey Fusion
Tips and ideas for editing game engines for Half-Life, the Quake Series, Red Faction, and the Unreal Series.

Crosshair Central
Provides crosshairs for Central, Quake 2, Half-Life, Counter-Strike, Sin, and Kingpin, tools, and tutorials.

Cooltech Games
Patches and modifications for Half-Life, Unreal Tournament, and Quake.

The Bullseye Crosshair Collection
Includes modifications for the Quake Series and Half-Life.

Gamelaunch 3D
Front-end for configuring 3D games. Contains news, downloads, and support.

Vondur's War Supply
Includes custom maps for Quake, Quake2, Quake 3 Arena and Half-Life.

Total Conversions.com
Deals with modifications to games developed by 3DRealms.

Super Capture the Flag
Includes game modifications, downloads and information. Plays on Quake and Half-Life.

Poly Count
Includes downloads, modifications and game resources.

Slacker's House
Unreal Tournament, Unreal Tournament 2003, and Quake 3 maps.

M Planet
Includes mapping and level editing instructions, and downloads.

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.

boodizm.net
Mods, maps, scripts, tutorials and utilities for Soldier of Fortune 2 and Quake 3 Arena.

VR21
Offers modifications and add-ons for several games, including Doom and Quake.

The Open Source Development Team
Contains maps for Counter Strike and Unreal Tournament 2003.

Ultimate Mapping
Maps for Counter Strike and Battlefield 1942.