Freeloading PC Multiplayer Party Games
Thanks to 1UP for its 'Freeloader' article profiling little-known but free multiplayer party games for the PC. The author explains of the featured games: "All of them are quick to download, easy on the system requirements, free of charge, and support six or more players. Perfect for the next time you throw together a quick gaming session", before pointing to Little Fighter 2 ("Super-deformed kids hitting each other in the face with baseball bats"), Soldat ("about as close as you can come to a side scrolling Quake deathmatch"), and Liquid War ("Definitely the most fun you'll have playing with puddles since you were six.")
Liquid war is one of the most fun open source games I've played. I'm surprised BZFlag wasnt mentioned!