Kquery looks like a quite nice alternative to Gamespy, which i"ve never really liked very much - even more now i know i can carry out DDoS with it...
"Kquery is a game server browser (reporting players, rules, maps, server settings, etc.) It"s a popular freeware alternative to Gamespy and All Seeing Eye, and supports Quake 3, Half Life, Unreal Tournament, Return To Castle Wolfenstein, Counter Strike, EF, Quake 2, JK2, MOHAA, and many more games."