aGSM!

Qtracker is an Internet/LAN game and MP3 server browser. If you want to find places to play your favorite games, look no further. You can also use Qtracker to administer your game servers, and generate HTML or PHP server listings.

A direct "like for like" replacement for the GameSpy MasterServer, and supports a huge number of games.333networks is the official MasterServer for several games companies, and can be self-hosted, or use the main Master, or both.