I’ll start the ball rolling. My inquiry concerns the Engorgement Charm, a way of enlarging any body part. I think I need not expound on the potential applications. So is using it for enhancement considered vulgar?
I wanna know if any of the students staying past their OWLs ever have to leave the school because they got knocked up…
I also wanna know about the “Hogwart’s Hoes.”
That could be the next series… 
As long as you don’t engorge yourself to freakish proportions, I don’t see any problem 
I wonder if something like Viagra exists in the magical world. I can see the advertisements now: “Is your wand not as rigid as it used to be? Is your marriage suffering because you can’t cast those ‘love spells’ like you could when you were 20? Ask your doctor for Wizagra[sup]TM[/sup].”
Fred Rogers vs. Barney the Dinosaur. Who wins?
Sorry, folks. That was supposed to be a new thread.
Dangit.
The invisible cloak. You KNOW it’s been used to peep at stuff.
What if you accidentally yelled a magic spell when you…would the spell become active? There’s the emotional component, right? I can see the problems there…
Who was the first to try an inter-species mating?
Somebody and a veela?
There’s some powerful enchantment on the school that prevents this. It’s in Hogwarts: A History. Hermione knows all about it, but she never tells anyone.
How do the non-muggle-born remain so steadfastly clueless about the real world? In the first movie, they didn’t know what guns were. “It’s a kind of wand the muggles use to kill each other.” How the hell did they not know what guns were??? “What is the significance of a rubber duck?” It’s a freaking toy, you boob!
I was gonna ask, what do all those tens of thousands of wizards you see in the stands for the Quiddich World Cup do for a living, but I think the previous questions have answered that question: they’re making Engorgio potions…
What vices do wizards enjoy? Since with magical medicine you’d assume that a hangover can be cured instantly, do they drink a lot? Does Herbology create a lot of stoner wizards?
Is birth control done magically? If so, do witches have periods or are they also stopped magically?
If birth control is magical, does the Catholic Church condone it or not?
Are the Weaslies Catholic? It seems they are a stereotype of Irish-Catholics, with the red-hair and the loads of children.
What Professors are married?
Did Dumbledore have children? With whom?
Has polyjuice potion ever been used to enter the opposite sex locker room/shower?
What keeps muggle parents(like Hermione’s) from telling everyone about magic?
Both Hagrid and Professor Trelawney have been shown overindulging in regular old booze. They both seem to have paid the usual price in hangovers for it, too, although neither one is known for magical skill.
Heck, you get a hair from the right person and you don’t even need to leave your bedroom.
I always wondered about that one. Perhaps some big time magical threats?
Oh, and the ‘naughty’ applications of magic just have to wait until “Harry Potter and the Morning Wood” 
So does everyone in the wizarding world have the proportions of Pamela Anderson and Tommy Lee? :eek:
I, in general, just want to know what the hell Hermione’s parents are doing this whole time. I think all we know about them is that they’re dentists. But they’re apparently nice, loving parents, so how come they don’t take a more active part in Hermione’s life? Why don’t we ever see them? We’ve seen more of Harry’s parents, and they’re dead.
I also want to know why the wizards don’t adapt some of the Muggle world’s inventions to their own purposes. Come on, e-mail is faster than owls. I know, I know – owls are more prosaic, but still.
Actually, the owls make sense for me. If you want to use email, you have to have a computer, and a phone line, and an ISP, and software, and muggle money, none of which most wizards have the first clue about. With owls, all you need is owls, mice, paper, envelopes, and money.
I think we’ve already had an answer, in the person of Andromeda Black Tonks.
Snape is about 36, as of the beginning of OotP (per JKR, in interviews).
Snape used to hang out with Bellatrix Lestrange in school (per Sirius in GoF). This doesn’t necessarily mean they’re the same age, but it does suggest they’re unlikely to be more than two or three years apart.
Bellatrix is Andromeda’s OLDER sister (per HBP), making Andromeda, at most, around 38 at the beginning of OotP.
Andromeda’s daughter has to be at least 22 at the beginning of OotP (18 when she finished school + 3 years of Auror training + 1 year as a qualified Auror).
Of course, I’m not sure JKR actually sat down to do the math on this one
There’s probably some kind of gag spell that stops them from blabbing to anyone not in the know. Easy compared to after-the-fact memory charms, which the Ministry uses so lavishly.
What I wonder is why wizards want to keep their existence a secret from Muggles. “They might want magical solutions to their problems!” So what? What else is magic good for? In Muggle society we have all kinds of problem-solving specialists – doctors, lawyers, engineers, financial consultants – we could easily accommodate a category of professional wizards, and pay them well.
I’ve always wondered what the wizards’ religion would be. (See this old thread: http://boards.straightdope.com/sdmb/showthread.php?t=190401)
And shovel, just to be accurate.