Picnik

I've plugged Picnick before but I just wanted to let you all know that it's even more awesome now then it was before and is offering even more zombie photo editing tools. Including no less than 6 distinct zombie flesh tones!
I tried to use Picnick in the off season (not October), and the zombifying option was under premium (pay) features. I'm now happy to report that this feature is currently available to everyone without making an account or paying. Here's what I was able to do in just a few minutes.

  I take a lot of enjoyment surprising my friends with zombified photos of them. If your persuasion leans more towards vampires, there's new tools for that too. enjoy! (Link)