Your favorite jokes

Everyday in Biology class, one person tells a joke. At the end of the week, we vote on the best. The Joke of the Weeks are eligible for Joke of the Month, then Joke of the year. So I'm just seeing if some of you can share your favorite jokes. Oh yeah, they have to be 'clean enough for school'.

*Thanks

Okay this is quite funny but you dont have to give it...

there were two nuns...
One of them was known as Sister Mathematical (SM),
and the other one was known as Sister Logical (SL).
It is getting dark and they are still far away from the convent.
SM: Have you noticed that a man has been following us for the past
thirty-eight and a half minutes? I wonder what he wants.
SL: It's logical. He wants to rape us.
SM: Oh, no! At this rate he will reach us in 15 minutes at the most!
what
can we do?
SL: The only logical thing to do of course is to walk faster.
SM: It's not working.
SL: Of course it's not working. The man did the only logical thing. He
started to walk faster, too.
SM: So, what shall we do? At this rate he will reach us in one minute.
SL: The only logical thing we can do is split. You go that way and
I'll go
this way. He cannot follow us both.
So the man decided to follow Sister Logical. Sister Mathematical
arrives at
the convent and is worried about what has happened to Sister Logical.
Then Sister Logical arrives.
SM: Sister Logical ! Thank God you are here! Tell me what happened!
SL: The only logical thing happened. The man couldn't follow us both,
so he
followed me
SM: Yes, yes! But what happened then?
SL: The only logical thing happened. I started to run as fast as I
could
and he started to run as fast as he could.
SM: And?
SL: The only logical thing happened. He reached me
SM: Oh, dear! What did you do?
SL : The only logical thing to do. I lifted my dress up.
SM: Oh, Sister! What did the man do?
SL: The only logical thing to do. He pulled down his pants.
SM: Oh, no! What happened then?
SL: Isn't it logical, Sister? A nun with her dress up can run faster
than
man with his pants down.

And for those of you who thought it would be dirty, shame on u

What do you get when you cross an elephant with a rhino? A 'Hell-if-I-know' (try not to pronounce the 'h' so it is 'ell-if-I-know')

2 nuns are in a car and a vampire jumps out into the middle of the road.
nun 1 says to the 2nd nun 'quick show him your cross!'
the 2nd nun rolls down the window and sticks her hesd out and says 'GAT OUT OF THE ROAD YOU TOOTHY GIT!!' =)

-In the newspaper it said 'Please look after your neighbours in the cold weather'. Our neighbour is an 87 year old woman - not once has she come round to check if we are alright. The lazy cow hasn't even taken in her milk for 2 weeks!
-I parked in a disabled space today and a traffic warden shouted to me 'Oi, what's your disability ?' 'Tourettes, now f*** off!” I said.

Ok not suitable for a classroom... but still funny.

For a link to 1000s of jokes (including those for the classroom): http://www.comedyontheweb.co.uk