Minecraft private Skin Center
Top-down multi-player zombie survival game
Rigs of Rods Multiplayer server
Multiplayer chat rooms built with Express + Socket.IO
GraphOX is awesome
Sublimity Gaming Dungeons - Loot
Simple server list with direct connect via scripts.
Best Pokemon fangame EVER.
Gameserver Installer/Startscript for HL1 and HL2 Games
Open Source Virtual World and MMOG Development Platform
A little side-scrolling game, written in JAVA.
Proxy for games that emulates network conditions like ping and lag.
Networked Jeopardy game
Simple Artificial Lag Generator
A multiplayer Blackjack game which works over the internet
Modular Minecraft server plugin - commands, events, ...
A multiplayer First-Person-Shooter game built in Java 3D