"In God we Trust"
Most of the time, for most atheists, the motto "In God We Trust" is more an annoyance than anything else: a reminder that a large portion of the country thinks of us as outsiders in some fundamental manner, doubting whether we share the same values of fairness and humanity. Most atheists dismiss the lawsuits to remove the phrase from currency, however, as simply being bad for the image of atheists. Similarly, "under God" in the Pledge is something that nags in the back of our minds more than it really bothers any but the most puritanical.
Most atheists do think it's wrong to put a religious slogan onto currency, but simply do not feel it's an issue worth fighting over. The slogan was added to paper currency decades ago, along with the addition to the Pledge of Allegiance. The slogan was minted on coins more than a hundred years ago, and changing it would do little to improve our lives. The Michael Newdows of the world disagree, and I give them a certain respect for standing up for what they believe, despite the meager hope of eliminating it in the foreseeable future. These circumstances make the argument over the motto something of a play battleground, the deistic side largely playing defense to an aggressive but doomed minority offense.
That may change. In God We Trust ~ America is an organization that lobbies to include the motto in town halls across America. So far, the founder Jacquie Sullivan lists 25 cities, largely in California, that have gone along with this agenda. The lobbying packet offered on the website is impressive: it toes the line of case law quite carefully, something that casual theists rarely accomplish. It is supported with legal opinion, an offer of free legal support to any community challenged on the motto, and points off support while avoiding any direct mention of the religious intent behind the motto. The reason most theists don't follow the law with their reasoning is because the reasoning of the law is opposed to their aims, and contrary to common sense. The Supreme Court has ruled that phrases such as "In God We Trust" and the "Under God" in the Pledge are Constitutional because they are essentially secular in nature and imply nothing about the religiosity of America beyond a historical reference.
The argument is strained at best. Many bona fide religions do not feature a deity, or have multiple deities. Claiming that a phrase specifically endorsing a trust in a deity is secular in nature pushes the limits of credulity on its face. Proponents of the phrase usually use it to argue for the religious nature of America rather than an example of ceremonial deism. Nevertheless, given that it's the current state of the law laid down by the Supreme Court, it's usable as precedent, provided one is careful to follow the prescribed reasoning for including it in whatever official function desired.
Some atheists have resorted to defacing currency, crossing out the "God" on the face of bills and in some extreme cases, abrading it from the surface of coins. Some have put in alternate mottos such as "In Reason We Trust" or (somewhat ironically) "E Pluribus Unum". These kinds of actions are also unlikely to be legally challenged, but it remains to be seen whether they are to become widespread. It's effort to ink out words on every piece of paper that crosses your palm, and personally my patience for doing that would be rather thin. For some, it isn't. And they'll be the ones out on the battleground, fighting for civil rights many of us aren't aware we actually need.
[picture is of my wife's town in Japan, where my children just spent six weeks. They went to school there through the third week of July, after finishing up American public school in June.]