Well, I considered making this a thread where you post the riddle without the answer, but I am mostly interested in getting riddles to try on others. Anyway, if you want to not post the answer or write it backwards to avoid spoilers, go 'head.
Mine is from the 11th hour:
“This eight letter word has “kst” in the middle, in the beginning, and at the end.”
The answer is(backwards typed) dnatstskni.
I’ve used this in schools and only one student has solved it.
What about you?
“inkststand”?
For Peepthis
Gosh, I’ve made two mistakes today with my posting. It’s “inkstand”.
I typed poorly backwards.
I’m not sure if this is exactly what you had in mind, but here’s what I thought of.
You have a standard six-sided die (i.e., equal probability of each number coming up). How many times do you expect to have to roll it before you get a six?
The answer is six. As to how to get that…well, you never asked for that, did you? 
I understood the riddle; I was just pointing out Mahaloth’s Porky Pig-esque encryption.
I kind of figured that out after Mahaloth’s post. But since I didn’t read the answer in his post I didn’t notice the typo. You can count it as a semi-whoosh.
50 Is my first
Nothing is my second
A snake makes my third
Then three parts a cross are reckoned
I am your past,
and you fear me in cold weather.
What am I?
Answer: Lost.
L = 50 in Roman numerals,
O = Symbol for nothing
S = Sound of a snake,
T = Parts of a cross.
Yay!
Three business men check into a hotel. The manager charges them $30, and they each pay ten. Later that night, the next shift comes in and notices that the three men were overcharged by 5 dollars, so he sends a bellhop to go give them their 5 dollars. However, the bell hop is corrupt (gasp) and takes 2 dollars for himself. So, he gets to the room and gives each guy 1 dollar. So: the guys each really paid nine dollars. 9 x 3 = 27. The bellhop has two dollars. 27 + 2 = 29. Where did the thirtieth dollar go?
The “27 +2” is meaningless, and misleading. 3 guys paid 9, OUT OF WHICH the bellhop got 2. 27 MINUS 2 might make sense there, but 27+2 doesn’t.
One of my favorite riddles; I couldn’t figure it out but it seems obvious when you know the answer.
**
What’s greater than God?
And worse than the devil?
Poor men have it and rich men want it.
If you eat it, you die.**
Let me see if I remember this right…three men reach into a closet that has three red hats and two blue hats, but none of them look at which hat they put on their head. The first man looks at the other two and says “I have no idea what hat I’m wearing.” The second one looks around and says the same. The third then remarks, “I know exactly what color hat I’m wearing.” What color are they each wearing?
…and I forget the answer off the top of my head. As I recall, it’s impossible for M1 or M2 to be looking at two blue hats, because then they’d HAVE to know they’re wearing a red.
ResIspa, is the answer:
M1: Blue
M2: Blue
M3: Red
Man One and Man Two would each see one red hat and one blue hat, each thinking they could possibly be wearing a red or blue hat, but since Man Three sees two blue hats, he must be wearing red.
Revtim, that’s an old one. The answer’s pretty good, but I won’t answer it in case you were trying to get other people to guess.
Nothing.
Nothing is greater than God.
Nothing is worse than the devil.
Poor men have nothing and rich men want nothing.
If you eat nothing, you die.
Although now that I think of it, you can be rich and still want stuff…
Spoil it!
I knew I never should have opened this thread. It’s going to keep me up all night!
What do you mean by ‘How many times you expect to have to roll it before you get a six’?
50%?
90%?
I know it’s a nitpick, but it is a mathematical riddle.
How about:
How many people do you need in a room before there’s a 50% chance that two of them have the same birthday?
(The answer is somewhere in the 20’s, but I don’t recall it exactly.)
This riddle is more interesting if you make the third man blind. It also tosses Nocturne’s answer out the window. And to make it even more twisted I’ll give you a hint: You don’t have to know what color hats the first two men are wearing.
I just thought of one of my all time favorite riddles. You have to use several plays on words (homonymns) to solve it. I doubt that anyone’ll get it if they haven’t heard it before but who knows.
A man in is in a room with no doors or windows nor any other entrances or exits. The only other items in the room besides the man are a table and a mirror. How does he get out?
And a slightly easier riddle:
A man is found dead in a room with 53 Bicycles. How did he die? And no, he wasn’t run over.
I’ll take the easy one. He was cheating at cards (bicycles)