In order for atheism to become ubiquitous, certain widespread perceptions must be addressed and shown to be in error, and certain stereotypes must be countered. Atheism is widely perceived to be something that is only for radical liberals who are far from the mainstream in both appearance and attitude. First and foremost, those who want atheism to be ubiquitous must drive home the point, in the minds of the masses, that atheism is value neutral. In other words, theists must come to understand that atheism is simply the lack of a belief in any deity, and that there are no socio-political-economic strings attached to the decision to become an atheist.
These perceptions and stereotypes are promoted by factions of each of the two camps in the so-called "culture war": (1) Ann Coulter, Bill O'Reilly, Glenn Beck et al., who certainly promote caricatures, innacurate perceptions, and outright falsehoods about atheists and atheism (one of them being that, if you're not a liberal, then you must be a theist), and (2) a sub-set of liberal atheists who are actively hostile to non-liberal atheists (I have seen, on more than a few occasions, liberal atheists telling non-liberal atheists that the latter are an illogical combination, or that, as non-liberals, they do not belong on an atheist message board, or that atheism is the natural "turf" of the former group). The assorted nonsense of the first group is already being countered by atheists. I would like to see the second group become more accepting of atheists of all political and social persuasions, so that these pernicious perceptions and stereotypes, which greatly retard the spread of atheism, in my opinion, disappear.
Logically, there are two possible ubiquitous atheism futures: (1) modernization converts everyone to liberalism, thereby undermining the very premise of this thread and destroying any self-imposed barriers to the masses accepting atheism, or (2) the perceptions and stereotypes that prevent many non-liberals from becoming atheists disappear. The former is extremely unlikely, in my opinion, because there will always be non-liberals, such as conservatives and libertarians, as long as there are humans: the desire for small, limited government, and many other non-liberal concerns---all of which are not at all incompatible with atheism---will always exist. Instead of ignoring promising non-liberals, or writing them off, as I have seen many liberal atheists do, there should be outreach to such individuals. Furthermore, non-liberals who are already atheists should be more vocal, and announce their existence as widely as possible.
Finally, I am not saying that liberalism, and a personal style that is outside of the mainstream, are bad. I am saying that it is bad when atheism is sincerely thought to be, politically, only for liberals, and socially, only for people who are outside the mainstream (when I tell people that I'm an atheist, I often encounter much surprise, because I don't have the "alternative" look). Since the promotion of diversity is one of the core principles of the liberal ethos, I sincerely hope that liberal atheists will welcome and support non-liberal atheists. :)