I worked as an intern for the Library of Congress a few years ago, filing the answers for this service. It's the Library of Congress's "Ask a Librarian" service. If you've made a serious effort to track down some piece of information (by serious, I mean you've googled it, and you've checked your libary) and it eludes you still, you can go there and put in the question and they'll give you the resources to find it. However, the less you demonstrate that you've already done research, the less interested they'll be in helping you. If you give them the names of the places you've already checked, they're more likely to go out of their way to give you detailed information.
Sometimes, if they decide that the question is interesting or easy, they'll even answer it themselves. Once a guy wrote in because his five-year-old daughter wanted to know if there was any animal starting with the letter "X".
X-ray fish. :)
(Note: I'm recommending this for serious writers, mainly. They're required to take everyone seriously, but if you write in for a fanfic or RP information, that's a pretty gross waste of gov't time. I remember someone who wrote in to ask how much a fairy would weigh on Planet Imaginary if her bones weighed such an amount and her hair fell down to her butt. Don't be that person!)