E.N. Publishing offers the first adventure of ZEITGEIST for free, but if you're curious to read how well it runs for actual gaming groups, or if you're interested in the campaign but won't be able to run it yourself, turn your eyes to some of these story hours.
I think it's kinda cool, having so many versions of the same basic plot, like watching 8 different directors' takes on the same Shakespeare play. And if you're running ZEITGEIST it's a great resource to see how other groups are handling the adventures.
These are the campaigns that are still being updated regularly.
Ajar: A game using Google Hangouts, currently in the middle of adventure three.