It’s really embarrassing how many of these are totally cracking me up. 
What’s a foot long and slippery?
A slipper!
What do you call a boomerang that doesn’t come back when you throw it?
A stick!
And I heard recently (on these boards, maybe?) that Goebbels always tried to keep Hitler away from the beer. Apparently, he was a mean drunk.
Daniel
Another Oldie but Moldy:
What state is high in the middle and round on both ends?
Ohio
This morning when I got up I shot an elephant in my pajamas.
I’ll never figure out how he fit in my pajamas.
Jim
What did one tomato say to the other tomato?Nothing. Tomatoes don’t talk.What do you say if someone steals your cheese?Hey! That’s nacho cheese!
Made this one up myself. What’s a pirate’s favorite video game?
DD-ARR!
I told this to my friend; she couldn’t breathe because she was laughing so hard. I think it’s the lameness of the joke that really carries it.
What did the grape say when the elephant sat on it?
Nothing. It just let out a little wine.
Why are pirates so cool?
I dunno, they just ARRRR
Where did the General keep his armies?
In his sleevies!
What did the Zen Master say to the hot dog vendor?
Make me one with everything.
dies
I once heard a joke that was funny for the same reason you mentioned, but I can’t remember what it was. 
He gives him a 20 and asks for change. The vendor says
change comes from within.
Contemplate: The Zen Master asks for a double scoop of chocolate though he know he only sells hotdogs.
Get it?
It’s an ice cream koan!
Why couldn’t the orchestra play The Messiah?
They couldn’t Handel it
Why couldn’t Beethoven find his teacher?
Because he was Haydn
A musician who couldn’t spell was expecting some guests, but had to rush out at the last second for some snacks. She wrote a note and stuck it on the door:
Gone Chopin. Be Bach in a minuet.
Okay, here’s another one, fresh from my kids, old by several decades at least.
Q: Why did Humpty Dumpty have a great fall?
A: To make up for a lousy summer.
*Funny Quotes: *
“This recipe is certainly silly. It says to separate two eggs, but it doesn’t say how far to separate them.” – Gracie Allen
“When you get to a fork in the road, take it.” Yogi Berra
*Not from memory but from an email I got: *
Marriage is not a word. It is a sentence a life sentence.
Marriage is very much like a violin after the sweet music is over, the strings are attached.
Marriage is love. Love is blind. Therefore marriage is an institution for the blind.
Marriage is an institution in which a man loses his Bachelor’s Degree and the woman gets her Masters.
Marriage is a thing which puts a ring on a woman’s fingerand two under the man’s eyes.
Marriage is not just a having a wife but also worries inherited forever.
**Another Email (from an Astrophysicist): **
Did you hear about the statistician who invented a device to measure the weight of trees?
It’s referred to as the log scale.
Old statisticians never die, they just undergo a transformation
Computer Resources: The major item of any budget, allowing for the acquisition of any capital equipment that is obsolete before the purchase request is released.
Publish or Perish: The imposed, involuntary choice between fame and oblivion, neither of which is handled gracefully by most faculty members.
I have that in a book of aphorisms (which is at home, not here at work), and it is all over the net, but I can’t find who it is attributed to.
This one actually makes sense. Yogi lives on a road that forms a loop. No matter which way you go at the fork, you’ll get to Yogi’s house.
Or Russian!
I know. Yogi is actually my favorite baseball player and maybe my favorite celebrity, even though he stopped playing before I was born. I actually met him when I was 12 and he was part owner of YooHoo. He is every bit as nice as everyone says he is and he is just a natural story teller.
Jim
Bigamy is when you have one wife too many. So is monogamy…
What’s a pirate’s favorite fast food joint?
ARRRR-by’s
What did one toilet say to another?
Do I look flushed?
Why do boy ghosts like girl ghosts?
Because they have booooo-bies
What did one casket say to another?
Is that you coffin? (coughin’)