The past few years it's been:
* take my birthday (or the closest workday) off from work
* cook breakfast or go to IHOP
* wander around Target
* visit the local used bookstore and B&N (they're across the street from one another)
* eat lunch out
* spend the rest of the day reading at home with the pets
* eat ice cream for dessert

I did throw a birthday/house warming party the year after I brought my house. It was fun but I have absolutely no plans to do it again.

I kinda totally ignore the day. I do try to spend it totally alone though. At least that way I'm with people I actually like.

I'm not an introvert, but usually just go out to dinner w/ a couple friends, b/c I tend to get really stressed about birthdays and all the hype and getting older and whatever. Last year one of my friends threw a party for me where we had over a bunch of ladies to watch a movie we both loved. Unfortunately, everyone there except me and one other person was pregnant or had a small child, so after spending way too much of the evening listening to people talk about pregnancy boobs, I left and drove home crying (I am a bitter single person who was once told to have kids before I was 28 due to various reproductive issues--and am now in my 30s).

I'm probably not going to celebrate my birthday this year (except for eating cupcakes of course), and am spending Christmas with the dvds of Community seasons 1 and 2. Sometimes it's just easier to be a misanthrope.

Also, happy almost birthday. :)

Chocolate.

Yep, best thing of all to make bdays worth it.

Well, back when I was single, I never told anyone, I'd field calls from family, and just hang out with the dogs and cat. Now that I'm married, my wife takes me out for dinner. Just the two of us, and then we go home, have some red wine, and hang out with the dogs and cats. That to me is the perfect way to celebrate my birthday.

And happy birthday eve.

As that apparently rare creature who is both introvert and extrovert as well as having unusual birthday date/day/month complications, I give you this advice:
It's your own personal holiday. If possible, do only what you want to do, liberally using the excuse that it is your birthday. People will give a lot of slack/excuse a lot of things in case of birthdays. Strange but true.
If you are celebrating on your somehow legally validated birthday, get all the free stuff you can. Free drinks, free food, weirdo freebies, they are all over the place. People will even create stuff on the spot for you. People are usually just looking for an excuse to use the amount of variance they are allowed in whatever position they have. We don't really haggle in the US but if you bother, you can get away with lots of stuff.
Indulge yourself, with no need for excuses. If there is something that definitely affords you unadulterated pleasure, do it. Start now, so you have recovery time if you have to do stuff on Monday.
You don't have to do anything you don't want to do. It can wait. All of it. Maybe not if you have to milk a cow, but even a cow can wait a little. Don't check your phone or your email or anything that feels like an obligation more than something you actually want to do.

Finally, use this day as a comparison for other days. If you actually got to do only what you wanted to do, felt free of obligation, got a little special treatment, figure out how much you enjoyed it and can incorporate it into your life if you like. So much is about priorities and choices and most people don't even know it.

Have fun.

I divide it between spending some time with my favorite people (immediate family)- nothing especially festive, just being around them- and spending whatever surplus money I have on a special experience that I do on my own. Skipping either part means that I miss out on something important, since those people are some of the best parts of my life, but treating my solo time as the actual celebration means that I can thoroughly enjoy it without worrying about keeping anybody else happy. This past year I took a train down to visit my sister and her family, and then stopped at a D.C. hostel overnight on the way back, spending a day wandering between museums and then going out for a ridiculously fancy dinner and drinking ALL THE WINES. It was marvelous.

I am completely in agreement with ethylene.

Yay, corroboration!
I am all about the fancy wines and museums.
When is your birthday?

I got the bestest card from gaspode, even metachat related, and I hope to one day impose upon her for museum access. I do love DC for museum access. Sigh. I considered living there for it.
I have been so long from museum access and that is really as I come close to church, when i am capable of it.

The mister's and my birthdays are close together (his is the 12th, mine is the 15th*) so we combine them. We don't usually do much. We exchange cards (not going to do that this year tho'), usually have a meal out (nothing fancy) and buy or make a cake. We may or may not go out to the movies or rent one. We're just happy to spend the day with each other.

*I'll be 45 years-old this year. That is so weird.

Forgot to mention gifts. We sometimes combine them with xmas, sometimes separately. Sometimes we do separate gifts, sometimes it's a big thing. 2009 we got the big screen TV and some DVDs as combined bday and xmas presents to ourselves. This year is gift-less - the mister is just about to switch from short-term to long-term disability. And that's fine. We're grown-ups and can deal with that as long as we're together. :)

My birthdays are much like eekacat described. Being on new year's day many people are hung over and many places are closed so low key is the order of the day.

Fuck yeah, happy birthday!

That's the best I got... (If I could make that little small text right here, that's what I would do)

happy birthday!

Well, I'm an introvert, but that doesn't mean I don't want a big party. Some years I do want a big party! I just need to make sure I can recover from it.

Other years, a couple friends, a day at the beach, and a margarita or two at dinner.