Peace be with you....or I'm already blessed indeed
I don't think a formal response or discourse is necessary.

Mu response to such staements is always to simply ignore them -- not respond at all (As if I did not hear them).

I say either" you too" or" same to you". If they know I'm atheist and keep telling me how much they pray for me, I retaliate with a sarcastic remark

I just ignore it, instead of getting into an argument with ignorant people. I consider it below me to do so and nothing is accomplished anyway.

The only one I will clearly react to is "I will pray for you". It's patronising and condescending and I will tell them why. One reply of mine was, don't pray for me, I don't want or need it. Pray for all the people your religion has hurt, or better yet, don't pray, do something about it. I make my anti theist position quite clear. Too bad if they are offended. I'm well beyond that.

I acknowledge and move on... if it made them feel good. Does not bother me. I got sisters deep into religion but they don't try to convert me. I been the same since a little child.

"thanks"

and I move on with my life.

"Thanks, I wish you well, too" is a pleasant, non-religious response.
A blessing can be non-religious, too.
It's an intention of goodness, whatever that means to the recipient.
I offer my personal blessing to people all the time.
Blessings,
hellskitchman

Thanks or Ok usually with a smile.

I accept their well-intentioned wishes for me and thank them.

"Thank you."

I usually just say thanks. It means they are thinking of me and/or my situation or just wishing me well. Religion is just the vehicle they use to express their empathy. I guess I am just trying to say its the thought that counts, not the delivery system.

I smirk, trying not to laugh at them, saying nothing.

I say “ thanks” because I’m their cultural construct they are wishing you well.

I just move on as I can't be assed anymore

I have to admit, coming from a southern baptist upbringing, the "bless you" after someone sneezes slips out occasionally. However, I usually catch myself, and it comes out as a mumbled "bless yyyy"... LoL

As to my replies, I usually say, thanks, or smile and nod. I try to take it good form as they are usually meaning well, however misguided it may be.

The "have a blessed day" thing does make me roll my eyes for some reason. So I usually ignore that one. I don't think I ever heard it until recently, so I am not sure if it is new or a geographical thing.

I am torn on the whole subject. I feel everyone should think whatever makes them happy. However, I feel that most evil in the world was/is caused by religion, and that it would be a much better place without it.

Regular people I just ignore. People I care about don't say it to me anymore even though they're all fundamentalist Christians. I've been godless for awhile. I guess I'm trying to say it fades with time. Hope some other comments help you out

I ignore and move along. I'm rarely in the mood for a discussion with one of the faithful about their faith or my lack thereof.

I ignore it and move on. Unless I’m in a bad mood I have responded with “F$&k you too”. But I have to be pissed to do that.