For those who still have a birthday upcoming, my 2012 cumulation:
All of these are accomplished on their respective web sites via a "birthday club" or some such sign up. Of course, you'll get other promotional offers during the year. Most are in the CBD.
Royal Oak Brewery
Give you a free entree (dine in). You need to register at least the week before the month of your birthday. E-mail arrives on the 1st of the month and is good for that month.
Also offer a free entree, but their e-mails arrive a week before your birthday and are usually good for 14 days. Noodles lets you do a take-out, but Mongo wants you in a seat inside.
I had a very nice tour of craft beers offered by these places as I celebrated my birthday. I didn't cook for a week.
You can finish off one of these repasts in downtown Royal Oak with a single scoop of ice cream at Baskin-Robins via their Birthday Club sign-up. Cold Stone Creamery used to have the same thing, but now it's a buy-one-get-one coupon.
Quodoba had one I didn't use, I think it was buy a burrito, get one, their standard promotional offer.
will give you a small (4 section) pizza. I go to the one on Woodward. It's dine-in if you go to one of their sit-down eateries.
A little further away, Red Robin on John R will give you a free, fat-and-salt laden burger (good!), but you need to do a little work: pick up a customer card at the restaurant first, then register it when you sign up for the birthday offering online. It will be loaded with the free burger a week before your birthday (good for the rest of the month, I think). Yes, Carter, they have beer there too.
Finally, Lilli's has a birthday club which rewards you with an entree when you dine in with somebody who also buys an entree. I just signed up for this one so I don't know if this is a standard promotional special or not. I do know they invited me to Tartan Day and I'm waiting to see what other national pride days they celebrate.
I Googled "free on your birthday" for surrounding cities and our Entertainment District Downtown was the clear leader in number of offers.
Any others to register for during the rest of the year would no doubt be used by the rest of the crowd. Keep 'em coming!