I think you'd snag a pretty big audience if you had a commercial during the show Family Guy. Or better yet, find out when a good zombie movie is airing on TV and try to get a time slot during that.
You're really gettin' into the big deal now, guys! :)
You'd be getting members by the hundreds if you put the commercial on the Sci-Fi channel. I'm not particularly a big fan of the channel but I'm sure that if the watchers like genetically enhanced snakes and hordes of giant spiders they'll like a Community Generated Zombie Documentary.
Adult Swim would bag tons of watchers, and Sci-Fi would probably be just as good, and definitely a lot more appropriate. It would be easy to work it into any of their undead marathons.