The Dead Roo pointed me at the Blasphemy Challenge - record a YouTube video including the phrase "I deny the Holy Spirit", and get a free atheist DVD (or if you're not American, a much cheaper one). You can see some of the responses (including those from outraged Christians) here.
How you feel about this will obviously depend on your view of atheism. Those who want to profess their lack of faith or piss off the Christians will leap at it, and I can see the appeal in that. But I'm simply not that kind of atheist any more. Religion is simply irrelevant to my life, except insofar as those with imaginary friends try to impose them on me (which fortunately doesn't happen very often in New Zealand). Sure, I deny the holy spirit, just as I deny the flying spaghetti monster, fire-breathing dragons, ghosts, Great Cthulhu, or any of the other fictional props which form a backdrop to my preferred entertainments. But I don't waste my time thinking about it on a daily basis. That's no reason not to do it, of course, but going to the effort of recording a video saying so just seems to be caring too much about something which doesn't matter to me in the slightest.