Would you kindly direct your browser to the excellentwww.talesofworldwarz.com
There is a tonne of excellent free Zombie short stories, serialisations and wizards. Ok, I may have lied about the wizards.
They set a high standard for submissions posting a couple a month from out of about 100 a month received so the overall quality is very good.
I may also have *ahem* a few tales of mine up there...*ahem*...even so, its still worth checking out.
(First one to get the videogame reference in this post wins a truckload of internet tubes)