One time an idiot was at a vending machine. He would stick a quarter in, push the button, a soda would come out and he would put it on top of the machine. He did this a few more times before a man asked why he kept doing this, and he said, "Because I'm winning."
Here are some randomly selected joke topics
Doctors
Doctor: How did you get here so quickly?
Patient: Flu.
Baker
Why did everyone find the bakers jokes funny?
Because he had a rye sense of humor.
Personality
Patient: Doctor, doctor, I think I'm developing a split personality.
Doctor: Well, sit down, both of you.
Drunks
I knew that I must be drunk when I started feeling sophisticated - and couldn't pronounce it.
Cat
Knock Knock
Who's There
Cat
Cat Who
Caterpilla
Know
Do you know me?
Yes, of course I know you.
Knock knock.
Who's there?
I thought you knew me!
Policeman
What did the policeman say to his belly-button?
You're under a vest.
Vacation
His mind is on vacation but his mouth is working overtime.
Stupid
He's so stupid he doesn't get dandruff - he gets sawdust.