Zombie Panic Source is a "Source Mod" that pits a team of up to 17 survivors and 3 zombies against each other. The objectives vary between maps and can range from blow up the zombie "house" to just plain survive for ten minutes. I played quite a bit and I can't stop playing. Enclosed are some screenshots for your entertainment including a mass zombie migration to "zombie island".

These next shots are of a guy who was infected by the carrier zombie (in this game the carrier is called "Whitey") who decided to help his team by leaving the base (knowing he was going to die) equipped with only a golf club. He lasted nearly 30 seconds.