Like: who are all the Dopers who live in NYC, for example? I know I can ASK, but they might not see it, so I was wondering if any thread had ever done that, or some such.
(In this case, I happen to be going to NYC in the near future, and I was wondering who lived there that I might want to buy a drink for. And I might be going to Northern Cal soon, etc.)
There were a few threads on this in the past.
Let’s see how many states/countries/provinces we have people here from.
Southern USA Dopers: Stand and be counted, please
Non-USA Dopers: Stand and be counted. Please.
Also, there’s this:
Frappr SDMB Map (USA Only)
There may be others that I am sure other Dopers remember.
Well, I am in NYC so if you wanted to buy me a drink I could be down with that. 
Can’t speak for anyone else though.
If you have plenty of time on your hands, you can go through members’ profiles one by one. For example, you can start with the page for velvetjones and subsequently change the number 8888 to 8887, 8886, and so forth, then eventually type in 8889 and move forward until you reach the newest joiner. Of course, the usefulness of this exercise is limited by the fact that some Dopers leave the location field blank, list fictitious places, or move from one area to another without updating the relevant info.
Their is no easy way to do this. You can’t even use the members list, because it’s too easy for undesirables to use the list for evil purposes. You will have to look up every profile, and then I think most members don’t list their location.
Another problem is that doing that will give you no real sense of who the active members are. The member numbers keep increasing, and once a number is used, it’s not re-used even if the Doper leaves the board. For example, former member reeder is member number 11506, and you can find his profile page, but he hasn’t posted here since February 2005.
So going through all those numbers would give you literally thousands of results for people who are no longer active members, and in some cases for people who may never have been active members, in the sense of actually posting on a regular basis.
I think your best bet is to start a post in MPSIMS with the title “NY Dopers! Can I buy you a drink?”
I’d swear that there was something similar to this that someone put together, a long long time ago, so I’m sure it’d be useless now. The Frappr thing is pretty cool, though. Someone should put that in a thread to get more people in it.
USA only? It looks to me just that not many rest-of-worlders have bothered.