SeriousZone is currently hosting these multiplayer servers:

Serious Sam Classic: The First Encounter

-SeriousZone.com Coop Server [CZE] - Classic Coop server, Normal difficulty, Friendly Fire, Infinite Ammo, 15 slots
-SeriousZone.com Shotty Temple <3 - DM server, no frag and time limit, Infinite Ammo, DB Shotgun only, 15 slots

Serious Sam Classic: The Second Encounter

-SeriousZone.com Coop Server [CZE] - Classic Coop server, Normal difficulty, Friendly Fire, Infinite Ammo, 15 slots
-SeriousZone.com Shotty Server [CZE] - DM server, limit 30 frags and no time limit, Infinite Ammo, DB Shotgun only, 15 slots
-SeriousZone.com Snipers Server [CZE] - DM server, limit 50 frags and no time limit, Infinite Ammo, Sniper only, 15 slots

Serious Sam HD: The First Encounter

-SeriousZone HD TFE (COOP) - Classic Coop server, Hard difficulty , 16 slots
-SeriousZone HD TFE (DM) - DM server, limit 40 frags, time 25 minutes, 8 slots
-SeriousZone HD TFE (Duel) - DM 1v1 server, limit 20 frags, time 15 minutes, 2 slots

Serious Sam HD: The Second Encounter

-SeriousZone HD TSE (COOP) - Classic Coop server, Hard difficulty , 16 slots

Serious Sam 3: BFE

-SeriousZone BFE (COOP) - Standard Coop server, Hard difficulty , 16 slots

Serious Sam Fusion 2017 (beta)

-SeriousZone Fusion (COOP) - Standard Coop server, Hard difficulty , 16 slots