It got started when someone in my town saw a documentary of it on Comcast OnDemand. The documentary is also on google video here It's a long video but watch it anyway!
Basically you start off with one zombie (Original Zombie, OZ) and a huge team of humans. We played with roughly 30 people, which is small compared to normal numbers.
The original zombie goes around and tries to tag people to make them zombies. Humans can stun zombies for 15 minutes by shooting them with Nerf guns or beating them with socks and sock swords. (Don't ask me why we use socks, it was a rule in the original game that we adopted)
The OZ (Original Zombie) can't die or be stunned until they record at least one kill. (Humans are defenseless until the OZ finally gets someone. Then it's open season.) Whe a human is tagged, they become a zombie after a 30 minute "transformation". Zombies die off after going 48 straight hours without recording a kill.
To make the game more challenging, a mission is created each day which MUST be completed by the humans. If not, they must sacrifice one of their own to the zombie horde. An example of a mission would be escorting a neutral person to a safe location without having that person tagged by a zombie or getting tagged yourself.
Now this may sound ridiculous and stupid, but trust me, this game is insane and can definitely bring some life to the generally boring town you live in.

The game is played mainly with Nerf guns. Some of the more savvy players like me mod their guns. I found though that Nerf guns can be inadequate when engaging zombies at longer range or several at close range. For close range, sock swords are the weapon of choice. So I set out to build a single weapon that could do it all.
I was messing around with ideas for single shot pneumatics until I got frustrated, bored, and picked up a piece of 1/2" PVC and started using it as a Nerf blowgun. To my surprise, it was deadly accurate and more powerful than any Nerf gun. That took care of my long range needs, but what do I do for close range? I decided to construct a sword based around 1/2" PVC so it can also be used as a blowgun.
My first sword turned out great but it was a little too heavy to be used effectively. The weight also made it dangerous. I used 1" PVC fittings to make a handle and 1/2" pipe as the core of the "blade". I wrapped the core in 7/8" foam pipe insulation for safety. I then wrapped it in a sock to conform to the stupid rules.

My second sword came out great too. This time I focused on minimizing the weight and I shortened it to 36" instead of the previous 42". I used 1/2" PVC sleeved in 1/2" copper insulation (TIGHT fit). I then took 1-1/2" x 8" plastic tailpiece (from a sink drain) and fit it around the insulation to make a handle. (Also TIGHT fit) I put a coupling on the 1/2" to form a simple mouthpiece. And of course, I attached socks. I had a Ronin Gear 12 gram CO2 cartridge wrist holder to make a 5 dart quiver.

Seriously, try this. And use a sword/blowgun. It's a great weapon.