My feelings exactly. It’s always astounded me that some religious people would prefer that i pretend to believe, rather than that i was honest. Given that most religions that i know value honesty, this seems a rather odd position to take.
A secular amen to that. 
I usually say “Bless the hands that made this food, and bless the hands that paid for it.”
It might have been cute when I came up with it at the tender age of eight, but I’m not sure how well traditionalists would appreciate it coming from my twenty-two year old, tattooed, pierced, High Priestess self.
Good point. Although I respect everyone’s right to have religious beliefs, I generally don’t respect the beliefs in question at all. Being asked to thank a supernatural entity for my food via prayer strikes me as akin to being asked to give thanks by sacrificing a chicken to Quahog The Cheese Spirit prior to a meal. I’ll happily do both if I’m eating with either group if it makes 'em happy. In each case, I’m akin to an anthropologist in the field with superstitious natives.
I have had this happen once to me, by surprise.
A little background; I’m Jewish by upbringing but agnostic by nature. Way back when in high school, as a gag, I sent my postcard to the Universal Life Church and got a certificate making me an Official Minister of the ULC. Says that I can perform weddings, funerals and other such ceremonies.
About 15 years later two of my very good friends decided to get married and asked me to officiate at their wedding (they knew about the ULC thing). I checked the laws and in SF county it’s completely cool, so we went ahead with the planning.
OK, so then we have the rehearsal dinner. The two extended families are in, we are all meeting & greeting and having a good time. Groom’s family puts on a big dinner at a restaurant.
We sit down to eat and suddenly the groom’s Mom says “Reverend, will you lead us in grace?” 50 pairs of eyes are on me.
Gulp. Think “Deer caught in the headlights”. Right then, the bride’s sister (only other person who happened to know what variety of ministerial credentials I hold), who was sitting next to me, whispered very quietly “Wing it, Rev!”.
Which is what I did - I’ve had dinner with families who say grace before so we all joined hands, bowed our heads, and I said something like “Dear Lord, we thank you for the presence of our friends and family and for the food that we are about to receive. Amen.” Came off pretty well I think. Bride and Groom thought this was hilarious afterwards.
The point here is that I knew that the families didn’t know I wasn’t a religious fellow and I was being asked to perform a small but important duty, and that this is intended as a compliment to the person being asked to say grace, not a way to put them on the spot or something.
Given this I think that it would have been awfully rude for me to decline, and I was able to improvise a perfectly acceptable grace and avoid anyone being embarassed (family members or myself). I certainly didn’t feel like it changed my spiritual outlook or betrayed my beliefs or anything - this was simply being courteous and respectful towards them and the occasion.
The right response would vary a bit depending on the circumstances, but I can’t see why the previously mentioned “We are thankful for the blahdeeblahdeeblah…” wouldn’t be fine just about anywhere, regardless of your personal beliefs.
If you really don’t want to say grace for whatever reason I think that the best response would be to say “I’m sorry, I don’t know how, could Joe do the honors?” You can tell the person your reason later. If they were to intentionally try and put you on the spot after that, I’d give the same excuse and then rethink any invites I got from those people.
I don’t think that a snappy comeback or a flat “No” is OK though, it’s taking offense when none was meant and it’s rude - sort of like giving a clerk a lecture on religious sensitivity if they say “Merry Christmas” when you buy something in December.
And the wedding went off without a hitch. Wonderful ceremony on a yacht in the SF bay 
That is a very good point. And if that’s your philosophical belief, then by all means just politely decline.
E.C., I think that the issue is really one of polite social behavior, and you’re right with the “making 'em happy” bit. If somebody doesn’t know how to say grace, or has stage fright, or is simply so repulsed by any religious connotations that it gives them Hideous Purple Hives, there are perfectly polite ways to not say grace. If you do this then it still behooves you to bow your head or hold hands or be silent for a moment or whatever it is that they are all doing, because you’re just showing some respect for your hosts and their beliefs, not adopting their religious practices.
If you were invited to a wedding and the priest said “We will now bow our heads and pray Jesus to bless this couple”, bowing your head and keeping quiet doesn’t mean you are praying, just that you’re respecting the ceremony. Meditate, ask Buddha to bless 'em, think about sports or have vivid fantasies about Elle McPherson and a big jar of honey, it’s all good, but going out of your way to say “I don’t believe in this stuff so I’m going to be noisy right now” would just be obnoxious.
Note that none of this applies if somebody knows that you are an atheist and keeps trying to get you to say grace. Then they are being rude. Same goes if it’s something way out in left field (“We say grace to Hitler, would you lead?”).
Shortest one yet:
"God’s neat, let’s eat. Amen.
I use Praise the Lord, and pass the food for informal dinners with well-known people.
For what we are about to receive, may we be truly grateful for more formal times and unknown beliefs at the table.