PF, the leper joke is my new favourite! Here's another:

A night in the barn
Jack decided to go skiing with his buddy, Bob. So they loaded up
Jack's mini van and headed north.
After driving for a few hours, they got caught in a terrible
blizzard. So they pulled into a nearby farm and asked the attractive
lady who answered the door if they could spend the night.
"I realize it's terrible weather out there and I have this huge house
all to myself, but I'm recently widowed," she explained. "I'm afraid
the neighbors will talk if I let you stay in my house."
"Don't worry," Jack said. "We'll be happy to sleep in the barn. And
if the weather breaks, we'll be gone at first light." The lady
agreed, and the two men found their way to the barn and settled in
for the night.
Come morning, the weather had cleared, and they got on their way.
They enjoyed a great weekend of skiing.
But about nine months later, Jack got an unexpected letter from an
attorney.
It took him a few minutes to figure it out, but he finally determined
that it was from the attorney of that attractive widow he had met on
the ski weekend.
He dropped in on his friend Bob and asked, "Bob, do you remember that
good-looking widow from the farm we stayed at on our ski holiday up
North about 9 months ago?"
"Yes, I do." said Bob
"Did you,, happen to get up in the middle of the night, go up to the
house and pay her a visit?"
"Well, um, yes," Bob said, a little embarrassed about being found
out. "I have to admit that I did."
"And did you happen to use my name instead of telling her your name?"
Bob's face turned beet red and he said, "Yeah, look, I'm sorry,
buddy. I'm afraid I did."
"Why do you ask?"
"She just died and left me everything."