Crosshair Central
- Provides crosshairs for Central, Quake 2, Half-Life, Counter-Strike, Sin, and Kingpin, tools, and tutorials.
- http://hosted.planethalflife.gamespy.com/cc/

Wavelength
- Focuses on editing and game modification in Half Life, Quake and Unreal series games. Includes downloads, tutorials and utility downloads.
- http://thewavelength.net/

VR21
- Offers modifications and add-ons for several games, including Doom and Quake.
- http://www.vr21.com/

Garjen Software
- Add-ons, custom levels and utilities for games such as Duke Nukem 3D, Wolfenstein, and Lemmings.
- http://www.garjen.co.uk/

Foyleman
- Soldier of Fortune, Serious Sam, and Return to Castle Wolfenstein.
- http://www.modsonline.com/

Slacker's House
- Unreal Tournament, Unreal Tournament 2003, and Quake 3 maps.
- http://slackerz.8m.com

Poly Count
- Includes downloads, modifications and game resources.
- http://polycount.com/

Super Capture the Flag
- Includes game modifications, downloads and information. Plays on Quake and Half-Life.
- http://www.sctf.net/

Total Conversions.com
- Deals with modifications to games developed by 3DRealms.
- http://www.TotalConversions.com

Vondur's War Supply
- Includes custom maps for Quake, Quake2, Quake 3 Arena and Half-Life.
- http://www.planetquake.com/vondur

The Bullseye Crosshair Collection
- Includes modifications for the Quake Series and Half-Life.
- http://www.bullseyecrosshairs.com/

Cooltech Games
- Patches and modifications for Half-Life, Unreal Tournament, and Quake.
- http://cooltech.rocketage.org/ctgames.htm

Grey Fusion
- Tips and ideas for editing game engines for Half-Life, the Quake Series, Red Faction, and the Unreal Series.
- http://www.greyfusion.net

DAV Levels
- Levels and maps for Doom2, Heretic, Hexen, Half-Life, Quake and Quake2.
- http://www.planetquake.com/davlevels/