Most of us do it, and there are many forums debating the issue of atheists 'taking the lords name in vain', so no need to rehash it here, unless you seriously feel the need...
I still fall back on 'Jeezus Christ' and goddamn thisorthat when I'm really flustered, but I've become more creative when I'm feeling squirrelly...
Darwin Dammit...By the bones of Galileo...or heebie Jebus momma...I still like Fuckit the best
For some reason, I always say "jesus tap-dancin' christ on a cross!!!" I say it when I'm so fucking pissed, then imagine the absurdness of jesus tap-dancin' on a cross...it makes me laugh my ass of, and all is better!! It's the whole blasphemy of it all...although I don't believe in blasphemy either since I believe in no god. I like to picture god as Flash Gordon, too, like on Family Guy...riding through space. Holy Flash Gordon...
I think there's no better way to spit on someone's religion than to use their god's name when cursing, so I'll still use them on the rare occasions that I feel I must curse.
At work, I often revert to what my mom taught me:
"God Bless America!" which can be pretty satisfying, believe it or not. Also, "Shit the Bed!" is good for when you fuck something up. I also belt out "Holy Flucking Snit" a lot.
But in good company, I am less creative: Fuck! Jesus Fucking Christ! Fucking Fuck! And so on...