ResLink
Automatic resolution changer for old games.

Microsoft DirectX
Libraries that are used by many Windows games.

Roger Wilco
Real-time voice chat for players on a network team.

GameRanger
Macintosh multiplayer online gaming service.

Kali
Allows play of IPX games over TCP-IP.

Alternative Game Server Monitor
A utility for Windows which locates and monitors game servers for many popular LAN and Internet games.

Apple Game Sprockets
Extensions for making games both easier to use and to develop thare are required to play many games.