Why not stand outside an Apple store and hand out DVDs under the motto 'here, free software for your new Mac'? Put LibreOffice, VirtualBox, Adium, and whatnot on it. Insert a flyer explaining what 'free software' means and suggest that they can donate to these projects if they like the software.
Sure, they will be running one OS X. But one step at a time is better than 99% thinking there were approached by nerd Hare Krishnas (nothing against Hinduism, it's about perception).